/*
 *  matiec - a compiler for the programming languages defined in IEC 61131-3
 *
 *  Copyright (C) 2009-2012  Mario de Sousa (msousa@fe.up.pt)
 *  Copyright (C) 2012       Manuele Conti (manuele.conti@sirius-es.it)
 *  Copyright (C) 2012       Matteo Facchinetti (matteo.facchinetti@sirius-es.it)
 *
 *  This program is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation, either version 3 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 *
 * This code is made available on the understanding that it will not be
 * used in safety-critical situations without a full and competent review.
 */

/*
 * An IEC 61131-3 compiler.
 *
 * Based on the
 * FINAL DRAFT - IEC 61131-3, 2nd Ed. (2001-12-10)
 *
 */


/*
 *  Fill candidate list of data types for all symbols
 */

#include "fill_candidate_datatypes.hh"
#include "datatype_functions.hh"
#include <typeinfo>
#include <list>
#include <string>
#include <string.h>
#include <strings.h>

/* set to 1 to see debug info during execution */
static int debug = 0;

fill_candidate_datatypes_c::fill_candidate_datatypes_c(symbol_c *ignore) {
}

fill_candidate_datatypes_c::~fill_candidate_datatypes_c(void) {
}

symbol_c *fill_candidate_datatypes_c::widening_conversion(symbol_c *left_type, symbol_c *right_type, const struct widen_entry widen_table[]) {
	int k;
	/* find a widening table entry compatible */
	for (k = 0; NULL != widen_table[k].left;  k++)
		if ((typeid(*left_type) == typeid(*widen_table[k].left)) && (typeid(*right_type) == typeid(*widen_table[k].right)))
			return widen_table[k].result;
	return NULL;
}


/* add a data type to a candidate data type list, while guaranteeing no duplicate entries! */
/* Returns true if it really did add the datatype to the list, or false if it was already present in the list! */
bool fill_candidate_datatypes_c::add_datatype_to_candidate_list(symbol_c *symbol, symbol_c *datatype) {
  if (search_in_candidate_datatype_list(datatype, symbol->candidate_datatypes) >= 0) 
    /* already in the list, Just return! */
    return false;
  
  /* not yet in the candidate data type list, so we insert it now! */
  symbol->candidate_datatypes.push_back(datatype);
  return true;
}
    
    
bool fill_candidate_datatypes_c::add_2datatypes_to_candidate_list(symbol_c *symbol, symbol_c *datatype1, symbol_c *datatype2) {
  add_datatype_to_candidate_list(symbol, datatype1);
  add_datatype_to_candidate_list(symbol, datatype2);
  return true;
}
    

/* returns true if compatible function/FB invocation, otherwise returns false */
/* Assumes that the candidate_datatype lists of all the parameters being passed haved already been filled in */
/*
 * All parameters being passed to the called function MUST be in the parameter list to which f_call points to!
 * This means that, for non formal function calls in IL, de current (default value) must be artificially added to the
 * beginning of the parameter list BEFORE calling handle_function_call().
 */
bool fill_candidate_datatypes_c::match_nonformal_call(symbol_c *f_call, symbol_c *f_decl) {
	symbol_c *call_param_value,  *param_datatype;
	identifier_c *param_name;
	function_param_iterator_c       fp_iterator(f_decl);
	function_call_param_iterator_c fcp_iterator(f_call);
	int extensible_parameter_highest_index = -1;
	unsigned int i;

	/* Iterating through the non-formal parameters of the function call */
	while((call_param_value = fcp_iterator.next_nf()) != NULL) {
		/* Iterate to the next parameter of the function being called.
		 * Get the name of that parameter, and ignore if EN or ENO.
		 */
		do {
			param_name = fp_iterator.next();
			/* If there is no other parameter declared, then we are passing too many parameters... */
			if(param_name == NULL) return false;
		} while ((strcmp(param_name->value, "EN") == 0) || (strcmp(param_name->value, "ENO") == 0));

		/* TODO: verify if it is lvalue when INOUT or OUTPUT parameters! */
		/* Get the parameter type */
		param_datatype = base_type(fp_iterator.param_type());
		
		/* check whether one of the candidate_data_types of the value being passed is the same as the param_type */
		if (search_in_candidate_datatype_list(param_datatype, call_param_value->candidate_datatypes) < 0)
			return false; /* return false if param_type not in the list! */
	}
	/* call is compatible! */
	return true;
}



/* returns true if compatible function/FB invocation, otherwise returns false */
/* Assumes that the candidate_datatype lists of all the parameters being passed haved already been filled in */
bool fill_candidate_datatypes_c::match_formal_call(symbol_c *f_call, symbol_c *f_decl, symbol_c **first_param_datatype) {
	symbol_c *call_param_value, *call_param_name, *param_datatype;
	symbol_c *verify_duplicate_param;
	identifier_c *param_name;
	function_param_iterator_c       fp_iterator(f_decl);
	function_call_param_iterator_c fcp_iterator(f_call);
	int extensible_parameter_highest_index = -1;
	identifier_c *extensible_parameter_name;
	unsigned int i;
	bool is_first_param = true;

	/* Iterating through the formal parameters of the function call */
	while((call_param_name = fcp_iterator.next_f()) != NULL) {
		/* Obtaining the value being passed in the function call */
		call_param_value = fcp_iterator.get_current_value();
		/* the following should never occur. If it does, then we have a bug in our code... */
		if (NULL == call_param_value) ERROR;

		/* Obtaining the assignment direction:  := (assign_in) or => (assign_out) */
		function_call_param_iterator_c::assign_direction_t call_param_dir = fcp_iterator.get_assign_direction();

		/* Checking if there are duplicated parameter values */
		verify_duplicate_param = fcp_iterator.search_f(call_param_name);
		if(verify_duplicate_param != call_param_value)
			return false;

		/* Obtaining the type of the value being passed in the function call */
		std::vector <symbol_c *>&call_param_types = call_param_value->candidate_datatypes;

		/* Find the corresponding parameter in function declaration */
		param_name = fp_iterator.search(call_param_name);
		if(param_name == NULL) return false;
		/* Get the parameter data type */
		param_datatype = base_type(fp_iterator.param_type());
		/* Get the parameter direction: IN, OUT, IN_OUT */
		function_param_iterator_c::param_direction_t param_dir = fp_iterator.param_direction();

		/* check whether direction (IN, OUT, IN_OUT) and assignment types (:= , =>) are compatible !!! */
		if          (function_call_param_iterator_c::assign_in  == call_param_dir) {
			if ((function_param_iterator_c::direction_in    != param_dir) &&
			    (function_param_iterator_c::direction_inout != param_dir))
				return false;
		} else if   (function_call_param_iterator_c::assign_out == call_param_dir) {
			if ((function_param_iterator_c::direction_out   != param_dir))
				return false;
		} else ERROR;
		
		/* check whether one of the candidate_data_types of the value being passed is the same as the param_type */
		if (search_in_candidate_datatype_list(param_datatype, call_param_types) < 0)
			return false; /* return false if param_type not in the list! */
		
		/* If this is the first parameter, then copy the datatype to *first_param_datatype */
		if (is_first_param)
			if (NULL != first_param_datatype)
				*first_param_datatype = param_datatype;
		is_first_param = false;
	}
	/* call is compatible! */
	return true;
}




/* Handle a generic function call!
 * Assumes that the parameter_list containing the values being passed in this function invocation
 * has already had all the candidate_datatype lists filled in!
 *
 * All parameters being passed to the called function MUST be in the parameter list to which f_call points to!
 * This means that, for non formal function calls in IL, de current (default value) must be artificially added to the
 * beginning of the parameter list BEFORE calling handle_function_call().
 */
/*
typedef struct {
  symbol_c *function_name,
  symbol_c *nonformal_operand_list,
  symbol_c *   formal_operand_list,

  std::vector <symbol_c *> &candidate_functions,  
  symbol_c &*called_function_declaration,
  int      &extensible_param_count
} generic_function_call_t;
*/
/*
void narrow_candidate_datatypes_c::narrow_function_invocation(symbol_c *fcall, generic_function_call_t fcall_data) {
void *fill_candidate_datatypes_c::handle_function_call(symbol_c *f_call, symbol_c *function_name, invocation_type_t invocation_type,
                                                       std::vector <symbol_c *> *candidate_datatypes,
                                                       std::vector <symbol_c *> *candidate_functions) {
  */
void fill_candidate_datatypes_c::handle_function_call(symbol_c *fcall, generic_function_call_t fcall_data) {
	function_declaration_c *f_decl;
	list_c *parameter_list;
	list_c *parameter_candidate_datatypes;
	symbol_c *returned_parameter_type;

	if (debug) std::cout << "function()\n";

	function_symtable_t::iterator lower = function_symtable.lower_bound(fcall_data.function_name);
	function_symtable_t::iterator upper = function_symtable.upper_bound(fcall_data.function_name);
	/* If the name of the function being called is not found in the function symbol table, then this is an invalid call */
	/* Since the lexical parser already checks for this, then if this occurs then we have an internal compiler error. */
	if (lower == function_symtable.end()) ERROR;
	
	/* Look for all compatible function declarations, and add their return datatypes 
	 * to the candidate_datatype list of this function invocation. 
	 *
	 * If only one function exists, we add its return datatype to the candidate_datatype list,
	 * even if the parameters passed to it are invalid.
	 * This guarantees that the remainder of the expression in which the function call is inserted
	 * is treated as if the function call returns correctly, and therefore does not generate
	 * spurious error messages.
	 * Even if the parameters to the function call are invalid, doing this is still safe, as the 
	 * expressions inside the function call will themselves have erros and will  guarantee that 
	 * compilation is aborted in stage3 (in print_datatypes_error_c).
	 */
	if (function_symtable.multiplicity(fcall_data.function_name) == 1) {
		f_decl = function_symtable.get_value(lower);
		returned_parameter_type = base_type(f_decl->type_name);
		if (add_datatype_to_candidate_list(fcall, returned_parameter_type))
			/* we only add it to the function declaration list if this entry was not already present in the candidate datatype list! */
			fcall_data.candidate_functions.push_back(f_decl);
		
	}
	for(; lower != upper; lower++) {
		bool compatible = false;
		
		f_decl = function_symtable.get_value(lower);
		/* Check if function declaration in symbol_table is compatible with parameters */
		if (NULL != fcall_data.nonformal_operand_list) compatible=match_nonformal_call(fcall, f_decl);
		if (NULL != fcall_data.   formal_operand_list) compatible=   match_formal_call(fcall, f_decl);
		if (compatible) {
			/* Add the data type returned by the called functions. 
			 * However, only do this if this data type is not already present in the candidate_datatypes list_c
			 */
			returned_parameter_type = base_type(f_decl->type_name);		
			if (add_datatype_to_candidate_list(fcall, returned_parameter_type))
				/* we only add it to the function declaration list if this entry was not already present in the candidate datatype list! */
				fcall_data.candidate_functions.push_back(f_decl);
		}
	}
	if (debug) std::cout << "end_function() [" << fcall->candidate_datatypes.size() << "] result.\n";
	return;
}


/* handle implicit FB call in IL.
 * e.g.  CLK ton_var
 *        CU counter_var
 */
void fill_candidate_datatypes_c::handle_implicit_il_fb_call(symbol_c *il_instruction, const char *param_name, symbol_c *&called_fb_declaration) {
	symbol_c *fb_type_id = search_varfb_instance_type->get_basetype_id(il_operand);
  	/* Although a call to a non-declared FB is a semantic error, this is currently caught by stage 2! */
	if (NULL == fb_type_id) ERROR;

	function_block_declaration_c *fb_decl = function_block_type_symtable.find_value(fb_type_id);
	if (function_block_type_symtable.end_value() == fb_decl)
		/* The il_operand is not the name of a FB instance. Most probably it is the name of a variable of some other type.
		 * this is a semantic error.
		 */
		fb_decl = NULL;
	
	/* The narrow_candidate_datatypes_c does not rely on this called_fb_declaration pointer being == NULL to conclude that
	 * we have a datatype incompatibility error, so we set it to fb_decl to allow the print_datatype_error_c to print out
	 * more informative error messages!
	 */
	called_fb_declaration = fb_decl;

	/* This implicit FB call does not change the value stored in the current/default IL variable */
	/* It does, however, require that the datatype be compatible with the input parameter of the FB being called. 
	 * If we were to follow the filling & narrowing algorithm correctly (implemented in fill_candidate_datatypes_c
	 * & narrow_candidate_datatypes_c respectively), we should be restricting the candidate_datatpes to the datatypes
	 * that are compatible to the FB call. 
	 * However, doing the above will often result in some very confusing error messages for the user, especially in the case
	 * in which the FB call is wrong, so the resulting cadidate datatypes is an empty list. In this case, the user would see
	 * many error messages related to the IL instructions that follow the FB call, even though those IL instructions may be perfectly
	 * correct.
	 * For now, we will simply let the narrow_candidate_datatypes_c verify if the datatypes are compatible (something that should be done
	 * here).
	 */
	if (NULL != prev_il_instruction)
		il_instruction->candidate_datatypes = prev_il_instruction->candidate_datatypes; 

	if (debug) std::cout << "handle_implicit_il_fb_call() [" << prev_il_instruction->candidate_datatypes.size() << "] ==> " << il_instruction->candidate_datatypes.size() << " result.\n";
}


/* a helper function... */
symbol_c *fill_candidate_datatypes_c::base_type(symbol_c *symbol) {
	/* NOTE: symbol == NULL is valid. It will occur when, for e.g., an undefined/undeclared symbolic_variable is used
	 *       in the code.
	 */
	if (symbol == NULL) return NULL;
	return (symbol_c *)symbol->accept(search_base_type);
}

/*********************/
/* B 1.2 - Constants */
/*********************/
/******************************/
/* B 1.2.1 - Numeric Literals */
/******************************/
#define sizeoftype(symbol) get_sizeof_datatype_c::getsize(symbol)

void *fill_candidate_datatypes_c::handle_any_integer(symbol_c *symbol) {
	int calc_size;

	calc_size = sizeoftype(symbol);
	if (calc_size <= sizeoftype(&search_constant_type_c::bool_type_name))
	        add_2datatypes_to_candidate_list(symbol, &search_constant_type_c::bool_type_name, &search_constant_type_c::safebool_type_name);
	if (calc_size <= sizeoftype(&search_constant_type_c::byte_type_name))
		add_2datatypes_to_candidate_list(symbol, &search_constant_type_c::byte_type_name, &search_constant_type_c::safebyte_type_name);
	if (calc_size <= sizeoftype(&search_constant_type_c::word_type_name))
		add_2datatypes_to_candidate_list(symbol, &search_constant_type_c::word_type_name, &search_constant_type_c::safeword_type_name);
	if (calc_size <= sizeoftype(&search_constant_type_c::dword_type_name))
		add_2datatypes_to_candidate_list(symbol, &search_constant_type_c::dword_type_name, &search_constant_type_c::safedword_type_name);
	if (calc_size <= sizeoftype(&search_constant_type_c::lword_type_name))
		add_2datatypes_to_candidate_list(symbol, &search_constant_type_c::lword_type_name, &search_constant_type_c::safelword_type_name);

	if (calc_size < sizeoftype(&search_constant_type_c::sint_type_name))
		add_2datatypes_to_candidate_list(symbol, &search_constant_type_c::sint_type_name, &search_constant_type_c::safesint_type_name);
	if (calc_size < sizeoftype(&search_constant_type_c::int_type_name))
		add_2datatypes_to_candidate_list(symbol, &search_constant_type_c::int_type_name, &search_constant_type_c::safeint_type_name);
	if (calc_size < sizeoftype(&search_constant_type_c::dint_type_name))
		add_2datatypes_to_candidate_list(symbol, &search_constant_type_c::dint_type_name, &search_constant_type_c::safedint_type_name);
	if (calc_size < sizeoftype(&search_constant_type_c::lint_type_name))
		add_2datatypes_to_candidate_list(symbol, &search_constant_type_c::lint_type_name, &search_constant_type_c::safelint_type_name);
	if (calc_size <= sizeoftype(&search_constant_type_c::usint_type_name))
		add_2datatypes_to_candidate_list(symbol, &search_constant_type_c::usint_type_name, &search_constant_type_c::safeusint_type_name);
	if (calc_size <= sizeoftype(&search_constant_type_c::uint_type_name))
		add_2datatypes_to_candidate_list(symbol, &search_constant_type_c::uint_type_name, &search_constant_type_c::safeuint_type_name);
	if (calc_size <= sizeoftype(&search_constant_type_c::udint_type_name))
		add_2datatypes_to_candidate_list(symbol, &search_constant_type_c::udint_type_name, &search_constant_type_c::safeudint_type_name);
	if (calc_size <= sizeoftype(&search_constant_type_c::ulint_type_name))
		add_2datatypes_to_candidate_list(symbol, &search_constant_type_c::ulint_type_name, &search_constant_type_c::safeulint_type_name);
	return NULL;
}




void *fill_candidate_datatypes_c::visit(real_c *symbol) {
	int calc_size;

	calc_size = sizeoftype(symbol);
	if (calc_size <= sizeoftype(&search_constant_type_c::real_type_name))
		add_2datatypes_to_candidate_list(symbol, &search_constant_type_c::real_type_name,  &search_constant_type_c::safereal_type_name);
	if (calc_size <= sizeoftype(&search_constant_type_c::lreal_type_name))
		add_2datatypes_to_candidate_list(symbol, &search_constant_type_c::lreal_type_name, &search_constant_type_c::safelreal_type_name);
	if (debug) std::cout << "ANY_REAL [" << symbol->candidate_datatypes.size() << "]" << std::endl;
	return NULL;
}



void *fill_candidate_datatypes_c::visit(integer_c *symbol) {
	handle_any_integer(symbol);
	if (debug) std::cout << "ANY_INT [" << symbol->candidate_datatypes.size()<< "]" << std::endl;
	return NULL;
}


void *fill_candidate_datatypes_c::visit(neg_real_c *symbol) {
	int calc_size;

	calc_size = sizeoftype(symbol);
	if (calc_size <= sizeoftype(&search_constant_type_c::real_type_name))
		add_2datatypes_to_candidate_list(symbol, &search_constant_type_c::real_type_name, &search_constant_type_c::safereal_type_name);
	if (calc_size <= sizeoftype(&search_constant_type_c::lreal_type_name))
		add_2datatypes_to_candidate_list(symbol, &search_constant_type_c::lreal_type_name, &search_constant_type_c::safelreal_type_name);
	if (debug) std::cout << "neg ANY_REAL [" << symbol->candidate_datatypes.size() << "]" << std::endl;
	return NULL;
}


void *fill_candidate_datatypes_c::visit(neg_integer_c *symbol) {
	int calc_size;

	calc_size = sizeoftype(symbol);
	if (calc_size <= sizeoftype(&search_constant_type_c::int_type_name))
		add_2datatypes_to_candidate_list(symbol, &search_constant_type_c::int_type_name, &search_constant_type_c::safeint_type_name);
	if (calc_size <= sizeoftype(&search_constant_type_c::sint_type_name))
		add_2datatypes_to_candidate_list(symbol, &search_constant_type_c::sint_type_name, &search_constant_type_c::safesint_type_name);
	if (calc_size <= sizeoftype(&search_constant_type_c::dint_type_name))
		add_2datatypes_to_candidate_list(symbol, &search_constant_type_c::dint_type_name, &search_constant_type_c::safedint_type_name);
	if (calc_size <= sizeoftype(&search_constant_type_c::lint_type_name))
		add_2datatypes_to_candidate_list(symbol, &search_constant_type_c::lint_type_name, &search_constant_type_c::safelint_type_name);
	if (debug) std::cout << "neg ANY_INT [" << symbol->candidate_datatypes.size() << "]" << std::endl;
	return NULL;
}


void *fill_candidate_datatypes_c::visit(binary_integer_c *symbol) {
	handle_any_integer(symbol);
	if (debug) std::cout << "ANY_INT [" << symbol->candidate_datatypes.size()<< "]" << std::endl;
	return NULL;
}



void *fill_candidate_datatypes_c::visit(octal_integer_c *symbol) {
	handle_any_integer(symbol);
	if (debug) std::cout << "ANY_INT [" << symbol->candidate_datatypes.size()<< "]" << std::endl;
	return NULL;
}



void *fill_candidate_datatypes_c::visit(hex_integer_c *symbol) {
	handle_any_integer(symbol);
	if (debug) std::cout << "ANY_INT [" << symbol->candidate_datatypes.size()<< "]" << std::endl;
	return NULL;
}


// SYM_REF2(integer_literal_c, type, value)
/*
 * integer_literal:
 *   integer_type_name '#' signed_integer
 * | integer_type_name '#' binary_integer
 * | integer_type_name '#' octal_integer
 * | integer_type_name '#' hex_integer
 */
void *fill_candidate_datatypes_c::visit(integer_literal_c *symbol) {
	symbol->value->accept(*this);
	if (search_in_candidate_datatype_list(symbol->type, symbol->value->candidate_datatypes) >= 0)
		add_datatype_to_candidate_list(symbol, symbol->type);
	if (debug) std::cout << "INT_LITERAL [" << symbol->candidate_datatypes.size() << "]\n";
	return NULL;
}

void *fill_candidate_datatypes_c::visit(real_literal_c *symbol) {
	symbol->value->accept(*this);
	if (search_in_candidate_datatype_list(symbol->type, symbol->value->candidate_datatypes) >= 0)
		add_datatype_to_candidate_list(symbol, symbol->type);
	if (debug) std::cout << "REAL_LITERAL [" << symbol->candidate_datatypes.size() << "]\n";
	return NULL;
}

void *fill_candidate_datatypes_c::visit(bit_string_literal_c *symbol) {
	symbol->value->accept(*this);
	if (search_in_candidate_datatype_list(symbol->type, symbol->value->candidate_datatypes) >= 0)
		add_datatype_to_candidate_list(symbol, symbol->type);
	return NULL;
}

void *fill_candidate_datatypes_c::visit(boolean_literal_c *symbol) {
 	symbol->value->accept(*this);
 	if (search_in_candidate_datatype_list(symbol->type, symbol->value->candidate_datatypes) >= 0)
		/* if an explicit datat type has been provided (e.g. SAFEBOOL#true), check whether
		 * the possible datatypes of the value is consistent with the desired type.
		 */
		add_datatype_to_candidate_list(symbol, symbol->type);
	else {
		/* Then only a literal TRUE or FALSE was given! */
		/* In this case, symbol->type will be NULL!     */
		add_2datatypes_to_candidate_list(symbol, &search_constant_type_c::bool_type_name, &search_constant_type_c::safebool_type_name);
	}
	return NULL;
}

void *fill_candidate_datatypes_c::visit(boolean_true_c *symbol) {
	add_2datatypes_to_candidate_list(symbol, &search_constant_type_c::bool_type_name, &search_constant_type_c::safebool_type_name);
	return NULL;
}

void *fill_candidate_datatypes_c::visit(boolean_false_c *symbol) {
	add_2datatypes_to_candidate_list(symbol, &search_constant_type_c::bool_type_name, &search_constant_type_c::safebool_type_name);
	return NULL;
}

/*******************************/
/* B.1.2.2   Character Strings */
/*******************************/
void *fill_candidate_datatypes_c::visit(double_byte_character_string_c *symbol) {
	add_2datatypes_to_candidate_list(symbol, &search_constant_type_c::wstring_type_name, &search_constant_type_c::safewstring_type_name);
	return NULL;
}

void *fill_candidate_datatypes_c::visit(single_byte_character_string_c *symbol) {
	add_2datatypes_to_candidate_list(symbol, &search_constant_type_c::string_type_name, &search_constant_type_c::safestring_type_name);
	return NULL;
}

/***************************/
/* B 1.2.3 - Time Literals */
/***************************/
/************************/
/* B 1.2.3.1 - Duration */
/************************/
void *fill_candidate_datatypes_c::visit(duration_c *symbol) {
	/* TODO: check whether the literal follows the rules specified in section '2.2.3.1 Duration' of the standard! */
	
	add_datatype_to_candidate_list(symbol, symbol->type_name);
	if (debug) std::cout << "TIME_LITERAL [" << symbol->candidate_datatypes.size() << "]\n";
	return NULL;
}

/************************************/
/* B 1.2.3.2 - Time of day and Date */
/************************************/
void *fill_candidate_datatypes_c::visit(time_of_day_c *symbol) {
	add_datatype_to_candidate_list(symbol, symbol->type_name);
	return NULL;
}

void *fill_candidate_datatypes_c::visit(date_c *symbol) {
	add_datatype_to_candidate_list(symbol, symbol->type_name);
	return NULL;
}

void *fill_candidate_datatypes_c::visit(date_and_time_c *symbol) {
	add_datatype_to_candidate_list(symbol, symbol->type_name);
	return NULL;
}

/**********************/
/* B 1.3 - Data types */
/**********************/
/********************************/
/* B 1.3.3 - Derived data types */
/********************************/
/*  signed_integer DOTDOT signed_integer */
// SYM_REF2(subrange_c, lower_limit, upper_limit)
void *fill_candidate_datatypes_c::visit(subrange_c *symbol) {
	symbol->lower_limit->accept(*this);
	symbol->upper_limit->accept(*this);
	
	for (unsigned int u = 0; u < symbol->upper_limit->candidate_datatypes.size(); u++) {
		for(unsigned int l = 0; l < symbol->lower_limit->candidate_datatypes.size(); l++) {
			if (is_type_equal(symbol->upper_limit->candidate_datatypes[u], symbol->lower_limit->candidate_datatypes[l]))
				add_datatype_to_candidate_list(symbol, symbol->lower_limit->candidate_datatypes[l]);
		}
	}
	return NULL;
}

/*  TYPE type_declaration_list END_TYPE */
// SYM_REF1(data_type_declaration_c, type_declaration_list)
/* NOTE: Not required. already handled by iterator_visitor_c base class */
/*
void *fill_candidate_datatypes_c::visit(data_type_declaration_c *symbol) {
	symbol->type_declaration_list->accept(*this);
	return NULL;
}
*/

void *fill_candidate_datatypes_c::visit(enumerated_value_c *symbol) {
	symbol_c *enumerated_type;

	if (NULL != symbol->type)
		enumerated_type = symbol->type;
	else {
		enumerated_type = enumerated_value_symtable.find_value(symbol->value);
		if (enumerated_type == enumerated_value_symtable.end_value())
			enumerated_type = NULL;
	}
	enumerated_type = base_type(enumerated_type);
	if (NULL != enumerated_type)
		add_datatype_to_candidate_list(symbol, enumerated_type);

	if (debug) std::cout << "ENUMERATE [" << symbol->candidate_datatypes.size() << "]\n";
	return NULL;
}


/*********************/
/* B 1.4 - Variables */
/*********************/
void *fill_candidate_datatypes_c::visit(symbolic_variable_c *symbol) {
	symbol_c *result = search_varfb_instance_type->get_basetype_decl(symbol);
	if (NULL != result)
		add_datatype_to_candidate_list(symbol, result);
	if (debug) std::cout << "VAR [" << symbol->candidate_datatypes.size() << "]\n";
	return NULL;
}

/********************************************/
/* B 1.4.1 - Directly Represented Variables */
/********************************************/
void *fill_candidate_datatypes_c::visit(direct_variable_c *symbol) {
	/* Comment added by mario:
	 * The following code is safe, actually, as the lexical parser guarantees the correct IEC61131-3 syntax was used.
	 */
	/* However, we should probably add an assertion in case we later change the lexical parser! */
	/* if (symbol->value == NULL) ERROR;
	 * if (symbol->value[0] == '\0') ERROR;
	 * if (symbol->value[1] == '\0') ERROR;
	 */
	switch (symbol->value[2]) {
	case 'X': // bit - 1 bit
		add_datatype_to_candidate_list(symbol, &search_constant_type_c::bool_type_name);
		break;

	case 'B': // byte - 8 bits
		add_datatype_to_candidate_list(symbol, &search_constant_type_c::byte_type_name);
		break;

	case 'W': // word - 16 bits
		add_datatype_to_candidate_list(symbol, &search_constant_type_c::word_type_name);
		break;

	case 'D': // double word - 32 bits
		add_datatype_to_candidate_list(symbol, &search_constant_type_c::dword_type_name);
		break;

	case 'L': // long word - 64 bits
		add_datatype_to_candidate_list(symbol, &search_constant_type_c::lword_type_name);
		break;

	default:  // if none of the above, then the empty string was used <=> boolean
		add_datatype_to_candidate_list(symbol, &search_constant_type_c::bool_type_name);
		break;
	}
	return NULL;
}

/*************************************/
/* B 1.4.2 - Multi-element variables */
/*************************************/
/*  subscripted_variable '[' subscript_list ']' */
// SYM_REF2(array_variable_c, subscripted_variable, subscript_list)
void *fill_candidate_datatypes_c::visit(array_variable_c *symbol) {
	/* get the declaration of the data type __stored__ in the array... */
	/* if we were to want the data type of the array itself, then we should call_param_name
	 * search_varfb_instance_type->get_basetype_decl(symbol->subscripted_variable)
	 */
	symbol_c *result = search_varfb_instance_type->get_basetype_decl(symbol);
	if (NULL != result) add_datatype_to_candidate_list(symbol, result);
	
	/* recursively call the subscript list, so we can check the data types of the expressions used for the subscripts */
	symbol->subscript_list->accept(*this);

	if (debug) std::cout << "ARRAY_VAR [" << symbol->candidate_datatypes.size() << "]\n";	
	return NULL;
}


/* subscript_list ',' subscript */
// SYM_LIST(subscript_list_c)
/* NOTE: we inherit from iterator visitor, so we do not need to implement this method... */
// void *fill_candidate_datatypes_c::visit(subscript_list_c *symbol)


/*  record_variable '.' field_selector */
/*  WARNING: input and/or output variables of function blocks
 *           may be accessed as fields of a structured variable!
 *           Code handling a structured_variable_c must take
 *           this into account!
 */
// SYM_REF2(structured_variable_c, record_variable, field_selector)
/* NOTE: We do not need to recursively determine the data types of each field_selector, as the search_varfb_instance_type
 * will do that for us. So we determine the candidate datatypes only for the full structured_variable.
 */
void *fill_candidate_datatypes_c::visit(structured_variable_c *symbol) {
	symbol_c *result = search_varfb_instance_type->get_basetype_decl(symbol);
	if (NULL != result) add_datatype_to_candidate_list(symbol, result);
	return NULL;
}

/************************************/
/* B 1.5 Program organization units */
/************************************/
/*********************/
/* B 1.5.1 Functions */
/*********************/
void *fill_candidate_datatypes_c::visit(function_declaration_c *symbol) {
	search_varfb_instance_type = new search_varfb_instance_type_c(symbol);
	symbol->var_declarations_list->accept(*this);
	if (debug) printf("Filling candidate data types list in body of function %s\n", ((token_c *)(symbol->derived_function_name))->value);
// 	il_parenthesis_level = 0;
	symbol->function_body->accept(*this);
	delete search_varfb_instance_type;
	search_varfb_instance_type = NULL;
	return NULL;
}

/***************************/
/* B 1.5.2 Function blocks */
/***************************/
void *fill_candidate_datatypes_c::visit(function_block_declaration_c *symbol) {
	search_varfb_instance_type = new search_varfb_instance_type_c(symbol);
	symbol->var_declarations->accept(*this);
	if (debug) printf("Filling candidate data types list in body of FB %s\n", ((token_c *)(symbol->fblock_name))->value);
// 	il_parenthesis_level = 0;
	symbol->fblock_body->accept(*this);
	delete search_varfb_instance_type;
	search_varfb_instance_type = NULL;
	return NULL;
}

/**********************/
/* B 1.5.3 - Programs */
/**********************/
void *fill_candidate_datatypes_c::visit(program_declaration_c *symbol) {
	search_varfb_instance_type = new search_varfb_instance_type_c(symbol);
	symbol->var_declarations->accept(*this);
	if (debug) printf("Filling candidate data types list in body of program %s\n", ((token_c *)(symbol->program_type_name))->value);
// 	il_parenthesis_level = 0;
	symbol->function_block_body->accept(*this);
	delete search_varfb_instance_type;
	search_varfb_instance_type = NULL;
	return NULL;
}



/********************************/
/* B 1.7 Configuration elements */
/********************************/
void *fill_candidate_datatypes_c::visit(configuration_declaration_c *symbol) {
	// TODO !!!
	/* for the moment we must return NULL so semantic analysis of remaining code is not interrupted! */
	return NULL;
}

/****************************************/
/* B.2 - Language IL (Instruction List) */
/****************************************/
/***********************************/
/* B 2.1 Instructions and Operands */
/***********************************/

/*| instruction_list il_instruction */
// SYM_LIST(instruction_list_c)
void *fill_candidate_datatypes_c::visit(instruction_list_c *symbol) {
	/* In order to fill the data type candidates correctly
	 * in IL instruction lists containing JMPs to labels that come before the JMP instruction
	 * itself, we need to run the fill candidate datatypes algorithm twice on the Instruction List.
	 * e.g.:  ...
	 *          ld 23
	 *   label1:st byte_var
	 *          ld 34
	 *          JMP label1     
	 *
	 * Note that the second time we run the algorithm, most of the candidate datatypes are already filled
	 * in, so it will be able to produce tha correct candidate datatypes for the IL instruction referenced
	 * by the label, as in the 2nd pass we already know the candidate datatypes of the JMP instruction!
	 */
	for(int j = 0; j < 2; j++) {
		for(int i = 0; i < symbol->n; i++) {
			symbol->elements[i]->accept(*this);
		}
	}
	return NULL;
}



/* | label ':' [il_incomplete_instruction] eol_list */
// SYM_REF2(il_instruction_c, label, il_instruction)
// void *visit(instruction_list_c *symbol);
void *fill_candidate_datatypes_c::visit(il_instruction_c *symbol) {
	if (NULL == symbol->il_instruction) {
		/* This empty/null il_instruction does not change the value of the current/default IL variable.
		 * So it inherits the candidate_datatypes from it's previous IL instructions!
		 */
		intersect_prev_candidate_datatype_lists(symbol);
	} else {
		il_instruction_c fake_prev_il_instruction = *symbol;
		intersect_prev_candidate_datatype_lists(&fake_prev_il_instruction);

		if (symbol->prev_il_instruction.size() == 0)  prev_il_instruction = NULL;
		else                                          prev_il_instruction = &fake_prev_il_instruction;
		symbol->il_instruction->accept(*this);
		prev_il_instruction = NULL;

		/* This object has (inherits) the same candidate datatypes as the il_instruction */
		symbol->candidate_datatypes = symbol->il_instruction->candidate_datatypes;
	}

	return NULL;
}



void *fill_candidate_datatypes_c::visit(il_simple_operation_c *symbol) {
	/* determine the data type of the operand */
	if (NULL != symbol->il_operand) {
		symbol->il_operand->accept(*this);
	}
	/* recursive call to fill the candidate data types list */
	il_operand = symbol->il_operand;
	symbol->il_simple_operator->accept(*this);
	il_operand = NULL;
	/* This object has (inherits) the same candidate datatypes as the il_simple_operator */
	symbol->candidate_datatypes = symbol->il_simple_operator->candidate_datatypes;
	return NULL;
}


/* | function_name [il_operand_list] */
/* NOTE: The parameters 'called_function_declaration' and 'extensible_param_count' are used to pass data between the stage 3 and stage 4. */
// SYM_REF2(il_function_call_c, function_name, il_operand_list, symbol_c *called_function_declaration; int extensible_param_count;)
void *fill_candidate_datatypes_c::visit(il_function_call_c *symbol) {
	/* The first parameter of a non formal function call in IL will be the 'current value' (i.e. the prev_il_instruction)
	 * In order to be able to handle this without coding special cases, we will simply prepend that symbol
	 * to the il_operand_list, and remove it after calling handle_function_call().
	 *
	 * However, if no further paramters are given, then il_operand_list will be NULL, and we will
	 * need to create a new object to hold the pointer to prev_il_instruction.
	 */
	if (NULL == symbol->il_operand_list)  symbol->il_operand_list = new il_operand_list_c;
	if (NULL == symbol->il_operand_list)  ERROR;

	symbol->il_operand_list->accept(*this);

	if (NULL != prev_il_instruction) {
		((list_c *)symbol->il_operand_list)->insert_element(prev_il_instruction, 0);	

		generic_function_call_t fcall_param = {
			/* fcall_param.function_name               = */ symbol->function_name,
			/* fcall_param.nonformal_operand_list      = */ symbol->il_operand_list,
			/* fcall_param.formal_operand_list         = */ NULL,
			/* enum {POU_FB, POU_function} POU_type    = */ generic_function_call_t::POU_function,
			/* fcall_param.candidate_functions         = */ symbol->candidate_functions,
			/* fcall_param.called_function_declaration = */ symbol->called_function_declaration,
			/* fcall_param.extensible_param_count      = */ symbol->extensible_param_count
		};
		handle_function_call(symbol, fcall_param);

		/* Undo the changes to the abstract syntax tree we made above... */
		((list_c *)symbol->il_operand_list)->remove_element(0);
	}

	/* Undo the changes to the abstract syntax tree we made above... */
	if (((list_c *)symbol->il_operand_list)->n == 0) {
		/* if the list becomes empty, then that means that it did not exist before we made these changes, so we delete it! */
		delete 	symbol->il_operand_list;
		symbol->il_operand_list = NULL;
	}
	
	if (debug) std::cout << "il_function_call_c [" << symbol->candidate_datatypes.size() << "] result.\n";
	return NULL;
}


/* | il_expr_operator '(' [il_operand] eol_list [simple_instr_list] ')' */
// SYM_REF3(il_expression_c, il_expr_operator, il_operand, simple_instr_list);
void *fill_candidate_datatypes_c::visit(il_expression_c *symbol) {
  symbol_c *prev_il_instruction_backup = prev_il_instruction;
//   il_parenthesis_level++;
  
  if (NULL != symbol->il_operand)
    symbol->il_operand->accept(*this);

  if(symbol->simple_instr_list != NULL)
    symbol->simple_instr_list->accept(*this);

//   il_parenthesis_level--;
//   if (il_parenthesis_level < 0) ERROR;
  
  /* Now check the if the data type semantics of operation are correct,  */
  il_operand = symbol->simple_instr_list;
  prev_il_instruction = prev_il_instruction_backup;
  symbol->il_expr_operator->accept(*this);
  il_operand = NULL;
  
  /* This object has the same candidate datatypes as the il_expr_operator. */
  symbol->candidate_datatypes = symbol->il_expr_operator->candidate_datatypes;
  return NULL;
}


void *fill_candidate_datatypes_c::visit(il_jump_operation_c *symbol) {
  /* recursive call to fill the candidate data types list */
  il_operand = NULL;
  symbol->il_jump_operator->accept(*this);
  il_operand = NULL;
  /* This object has the same candidate datatypes as the il_jump_operator. */
  symbol->candidate_datatypes = symbol->il_jump_operator->candidate_datatypes;
  return NULL;
}


/*   il_call_operator prev_declared_fb_name
 * | il_call_operator prev_declared_fb_name '(' ')'
 * | il_call_operator prev_declared_fb_name '(' eol_list ')'
 * | il_call_operator prev_declared_fb_name '(' il_operand_list ')'
 * | il_call_operator prev_declared_fb_name '(' eol_list il_param_list ')'
 */
/* NOTE: The parameter 'called_fb_declaration'is used to pass data between stage 3 and stage4 (although currently it is not used in stage 4 */
// SYM_REF4(il_fb_call_c, il_call_operator, fb_name, il_operand_list, il_param_list, symbol_c *called_fb_declaration)
void *fill_candidate_datatypes_c::visit(il_fb_call_c *symbol) {
	/* We do not call
	 * fb_decl = search_varfb_instance_type->get_basetype_decl(symbol->fb_name);
	 * because we want to make sure it is a FB instance, and not some other data type...
	 */
	symbol_c *fb_type_id = search_varfb_instance_type->get_basetype_id(symbol->fb_name);
	/* Although a call to a non-declared FB is a semantic error, this is currently caught by stage 2! */
	if (NULL == fb_type_id) ERROR;

 	function_block_declaration_c *fb_decl = function_block_type_symtable.find_value(fb_type_id);
	if (function_block_type_symtable.end_value() == fb_decl) 
		/* The fb_name not the name of a FB instance. Most probably it is the name of a variable of some other type. */
		fb_decl = NULL;

	/* Although a call to a non-declared FB is a semantic error, this is currently caught by stage 2! */
	if (NULL == fb_decl) ERROR;

	if (symbol->  il_param_list != NULL) symbol->il_param_list->accept(*this);
	if (symbol->il_operand_list != NULL) symbol->il_operand_list->accept(*this);

	/* The print_datatypes_error_c does not rely on this called_fb_declaration pointer being != NULL to conclude that
	 * we have a datat type incompatibility error, so setting it to the correct fb_decl is actually safe,
	 * as the compiler will never reach the compilation stage!
	 */
	symbol->called_fb_declaration = fb_decl;

	/* Let the il_call_operator (CAL, CALC, or CALCN) determine the candidate datatypes of the il_fb_call_c... */
	/* NOTE: We ignore whether the call is 'compatible' or not when filling in the candidate datatypes list.
	 *       Even if it is not compatible, we fill in the candidate datatypes list correctly so that the following
	 *       IL instructions may be handled correctly and debuged.
	 *       Doing this is actually safe, as the parameter_list will still contain errors that will be found by
	 *       print_datatypes_error_c, so the code will never reach stage 4!
	 */
	symbol->il_call_operator->accept(*this);
	symbol->candidate_datatypes = symbol->il_call_operator->candidate_datatypes;

	if (debug) std::cout << "FB [] ==> "  << symbol->candidate_datatypes.size() << " result.\n";
	return NULL;
}


/* | function_name '(' eol_list [il_param_list] ')' */
/* NOTE: The parameter 'called_function_declaration' is used to pass data between the stage 3 and stage 4. */
// SYM_REF2(il_formal_funct_call_c, function_name, il_param_list, symbol_c *called_function_declaration; int extensible_param_count;)
void *fill_candidate_datatypes_c::visit(il_formal_funct_call_c *symbol) {
	symbol->il_param_list->accept(*this);

	generic_function_call_t fcall_param = {
		/* fcall_param.function_name               = */ symbol->function_name,
		/* fcall_param.nonformal_operand_list      = */ NULL,
		/* fcall_param.formal_operand_list         = */ symbol->il_param_list,
		/* enum {POU_FB, POU_function} POU_type    = */ generic_function_call_t::POU_function,
		/* fcall_param.candidate_functions         = */ symbol->candidate_functions,
		/* fcall_param.called_function_declaration = */ symbol->called_function_declaration,
		/* fcall_param.extensible_param_count      = */ symbol->extensible_param_count
	};
	handle_function_call(symbol, fcall_param);

	if (debug) std::cout << "il_formal_funct_call_c [" << symbol->candidate_datatypes.size() << "] result.\n";
	return NULL;
}


//     void *visit(il_operand_list_c *symbol);


/* | simple_instr_list il_simple_instruction */
/* This object is referenced by il_expression_c objects */
void *fill_candidate_datatypes_c::visit(simple_instr_list_c *symbol) {
  if (symbol->n <= 0)
    return NULL;  /* List is empty! Nothing to do. */
    
  for(int i = 0; i < symbol->n; i++)
    symbol->elements[i]->accept(*this);

  /* This object has (inherits) the same candidate datatypes as the last il_instruction */
  symbol->candidate_datatypes = symbol->elements[symbol->n-1]->candidate_datatypes;
  
  if (debug) std::cout << "simple_instr_list_c [" << symbol->candidate_datatypes.size() << "] result.\n";
  return NULL;
}




// SYM_REF1(il_simple_instruction_c, il_simple_instruction, symbol_c *prev_il_instruction;)
void *fill_candidate_datatypes_c::visit(il_simple_instruction_c *symbol) {
  if (symbol->prev_il_instruction.size() > 1) ERROR; /* There should be no labeled insructions inside an IL expression! */
  if (symbol->prev_il_instruction.size() == 0)  prev_il_instruction = NULL;
  else                                          prev_il_instruction = symbol->prev_il_instruction[0];
  symbol->il_simple_instruction->accept(*this);
  prev_il_instruction = NULL;

  /* This object has (inherits) the same candidate datatypes as the il_simple_instruction it points to */
  symbol->candidate_datatypes = symbol->il_simple_instruction->candidate_datatypes;
  return NULL;
}


/*
    void *visit(il_param_list_c *symbol);
    void *visit(il_param_assignment_c *symbol);
    void *visit(il_param_out_assignment_c *symbol);
*/

/*******************/
/* B 2.2 Operators */
/*******************/
void *fill_candidate_datatypes_c::visit(LD_operator_c *symbol) {
	for(unsigned int i = 0; i < il_operand->candidate_datatypes.size(); i++) {
		add_datatype_to_candidate_list(symbol, il_operand->candidate_datatypes[i]);
	}
	if (debug) std::cout << "LD [" <<  il_operand->candidate_datatypes.size() << "] ==> "  << symbol->candidate_datatypes.size() << " result.\n";
	return NULL;
}

void *fill_candidate_datatypes_c::visit(LDN_operator_c *symbol) {
	for(unsigned int i = 0; i < il_operand->candidate_datatypes.size(); i++) {
		if      (is_ANY_BIT_compatible(il_operand->candidate_datatypes[i]))
			add_datatype_to_candidate_list(symbol, il_operand->candidate_datatypes[i]);
	}
	if (debug) std::cout << "LDN [" << il_operand->candidate_datatypes.size() << "] ==> "  << symbol->candidate_datatypes.size() << " result.\n";
	return NULL;
}

void *fill_candidate_datatypes_c::visit(ST_operator_c *symbol) {
	symbol_c *prev_instruction_type, *operand_type;

	if (NULL == prev_il_instruction) return NULL;
	for (unsigned int i = 0; i < prev_il_instruction->candidate_datatypes.size(); i++) {
		for(unsigned int j = 0; j < il_operand->candidate_datatypes.size(); j++) {
			prev_instruction_type = prev_il_instruction->candidate_datatypes[i];
			operand_type = il_operand->candidate_datatypes[j];
			if (is_type_equal(prev_instruction_type, operand_type))
				add_datatype_to_candidate_list(symbol, prev_instruction_type);
		}
	}
	if (debug) std::cout << "ST [" << prev_il_instruction->candidate_datatypes.size() << "," << il_operand->candidate_datatypes.size() << "] ==> "  << symbol->candidate_datatypes.size() << " result.\n";
	return NULL;
}

void *fill_candidate_datatypes_c::visit(STN_operator_c *symbol) {
	symbol_c *prev_instruction_type, *operand_type;

	if (NULL == prev_il_instruction) return NULL;
	for (unsigned int i = 0; i < prev_il_instruction->candidate_datatypes.size(); i++) {
		for(unsigned int j = 0; j < il_operand->candidate_datatypes.size(); j++) {
			prev_instruction_type = prev_il_instruction->candidate_datatypes[i];
			operand_type = il_operand->candidate_datatypes[j];
			if (is_type_equal(prev_instruction_type,operand_type) && is_ANY_BIT_compatible(operand_type))
				add_datatype_to_candidate_list(symbol, prev_instruction_type);
		}
	}
	if (debug) std::cout << "STN [" << prev_il_instruction->candidate_datatypes.size() << "," << il_operand->candidate_datatypes.size() << "] ==> "  << symbol->candidate_datatypes.size() << " result.\n";
	return NULL;
}

void *fill_candidate_datatypes_c::visit(NOT_operator_c *symbol) {
	/* NOTE: the standard allows syntax in which the NOT operator is followed by an optional <il_operand>
	 *              NOT [<il_operand>]
	 *       However, it does not define the semantic of the NOT operation when the <il_operand> is specified.
	 *       We therefore consider it an error if an il_operand is specified!
	 */
	if (NULL == prev_il_instruction) return NULL;
	for (unsigned int i = 0; i < prev_il_instruction->candidate_datatypes.size(); i++) {
		if (is_ANY_BIT_compatible(prev_il_instruction->candidate_datatypes[i]))
			add_datatype_to_candidate_list(symbol, prev_il_instruction->candidate_datatypes[i]);
	}
	if (debug) std::cout <<  "NOT_operator [" << prev_il_instruction->candidate_datatypes.size() << "] ==> "  << symbol->candidate_datatypes.size() << " result.\n";
	return NULL;
}


void *fill_candidate_datatypes_c::visit(S_operator_c *symbol) {
  /* TODO: what if this is a FB call ?? */
	symbol_c *prev_instruction_type, *operand_type;

	if (NULL == prev_il_instruction) return NULL;
	for (unsigned int i = 0; i < prev_il_instruction->candidate_datatypes.size(); i++) {
		for(unsigned int j = 0; j < il_operand->candidate_datatypes.size(); j++) {
			prev_instruction_type = prev_il_instruction->candidate_datatypes[i];
			operand_type = il_operand->candidate_datatypes[j];
			/* TODO: I believe the following is wrong! The data types of prev_instruction_type and operand_type DO NOT have to be equal.
			 * the prev_instruction_type MUST be BOOL compatible.
			 * I am not too sure about operand_type, does it have to be BOOL compatible, or can it be ANY_BIT compatible? Must check!
			 */
			if (is_type_equal(prev_instruction_type,operand_type) && is_ANY_BOOL_compatible(operand_type))
				add_datatype_to_candidate_list(symbol, prev_instruction_type);
		}
	}
	if (debug) std::cout << "S [" << prev_il_instruction->candidate_datatypes.size() << "," << il_operand->candidate_datatypes.size() << "] ==> "  << symbol->candidate_datatypes.size() << " result.\n";
	return NULL;
}


void *fill_candidate_datatypes_c::visit(R_operator_c *symbol) {
  /* TODO: what if this is a FB call ?? */
	symbol_c *prev_instruction_type, *operand_type;

	if (NULL == prev_il_instruction) return NULL;
	for (unsigned int i = 0; i < prev_il_instruction->candidate_datatypes.size(); i++) {
		for(unsigned int j = 0; j < il_operand->candidate_datatypes.size(); j++) {
			prev_instruction_type = prev_il_instruction->candidate_datatypes[i];
			operand_type = il_operand->candidate_datatypes[j];
			/* TODO: I believe the following is wrong! The data types of prev_instruction_type and operand_type DO NOT have to be equal.
			 * the prev_instruction_type MUST be BOOL compatible.
			 * I am not too sure about operand_type, does it have to be BOOL compatible, or can it be ANY_BIT compatible? Must check!
			 */
			if (is_type_equal(prev_instruction_type,operand_type) && is_ANY_BOOL_compatible(operand_type))
				add_datatype_to_candidate_list(symbol, prev_instruction_type);
		}
	}
	if (debug) std::cout << "R [" << prev_il_instruction->candidate_datatypes.size() << "," << il_operand->candidate_datatypes.size() << "] ==> "  << symbol->candidate_datatypes.size() << " result.\n";
	return NULL;
}


void *fill_candidate_datatypes_c::visit(S1_operator_c *symbol) {
	handle_implicit_il_fb_call(symbol, "S1", symbol->called_fb_declaration);
	return NULL;
}

void *fill_candidate_datatypes_c::visit(R1_operator_c *symbol) {
	handle_implicit_il_fb_call(symbol, "R1", symbol->called_fb_declaration);
	return NULL;
}

void *fill_candidate_datatypes_c::visit(CLK_operator_c *symbol) {
	handle_implicit_il_fb_call(symbol, "CLK", symbol->called_fb_declaration);
	return NULL;
}

void *fill_candidate_datatypes_c::visit(CU_operator_c *symbol) {
	handle_implicit_il_fb_call(symbol, "CU", symbol->called_fb_declaration);
	return NULL;
}

void *fill_candidate_datatypes_c::visit(CD_operator_c *symbol) {
	handle_implicit_il_fb_call(symbol, "CD", symbol->called_fb_declaration);
	return NULL;
}

void *fill_candidate_datatypes_c::visit(PV_operator_c *symbol) {
	handle_implicit_il_fb_call(symbol, "PV", symbol->called_fb_declaration);
	return NULL;
}

void *fill_candidate_datatypes_c::visit(IN_operator_c *symbol) {
	handle_implicit_il_fb_call(symbol, "IN", symbol->called_fb_declaration);
	return NULL;
}

void *fill_candidate_datatypes_c::visit(PT_operator_c *symbol) {
	handle_implicit_il_fb_call(symbol, "PT", symbol->called_fb_declaration);
	return NULL;
}


void *fill_candidate_datatypes_c::visit(AND_operator_c *symbol) {
	symbol_c *prev_instruction_type, *operand_type;

	if (NULL == prev_il_instruction) return NULL;
	for (unsigned int i = 0; i < prev_il_instruction->candidate_datatypes.size(); i++) {
		for(unsigned int j = 0; j < il_operand->candidate_datatypes.size(); j++) {
			prev_instruction_type = prev_il_instruction->candidate_datatypes[i];
			operand_type = il_operand->candidate_datatypes[j];
			if (is_type_equal(prev_instruction_type, operand_type) &&
					is_ANY_BIT_compatible(operand_type))
				add_datatype_to_candidate_list(symbol, prev_instruction_type);
		}
	}
	if (debug) std::cout <<  "AND [" << prev_il_instruction->candidate_datatypes.size() << "," << il_operand->candidate_datatypes.size() << "] ==> "  << symbol->candidate_datatypes.size() << " result.\n";
	return NULL;
}

void *fill_candidate_datatypes_c::visit(OR_operator_c *symbol) {
	symbol_c *prev_instruction_type, *operand_type;

	if (NULL == prev_il_instruction) return NULL;
	for (unsigned int i = 0; i < prev_il_instruction->candidate_datatypes.size(); i++) {
		for(unsigned int j = 0; j < il_operand->candidate_datatypes.size(); j++) {
			prev_instruction_type = prev_il_instruction->candidate_datatypes[i];
			operand_type = il_operand->candidate_datatypes[j];
			if (is_type_equal(prev_instruction_type, operand_type) &&
					is_ANY_BIT_compatible(operand_type))
				add_datatype_to_candidate_list(symbol, prev_instruction_type);
		}
	}
	if (debug) std::cout <<  "OR [" << prev_il_instruction->candidate_datatypes.size() << "," << il_operand->candidate_datatypes.size() << "] ==> "  << symbol->candidate_datatypes.size() << " result.\n";
	return NULL;
}

void *fill_candidate_datatypes_c::visit(XOR_operator_c *symbol) {
	symbol_c *prev_instruction_type, *operand_type;

	if (NULL == prev_il_instruction) return NULL;
	for (unsigned int i = 0; i < prev_il_instruction->candidate_datatypes.size(); i++) {
		for(unsigned int j = 0; j < il_operand->candidate_datatypes.size(); j++) {
			prev_instruction_type = prev_il_instruction->candidate_datatypes[i];
			operand_type = il_operand->candidate_datatypes[j];
			if (is_type_equal(prev_instruction_type, operand_type) &&
					is_ANY_BIT_compatible(operand_type))
				add_datatype_to_candidate_list(symbol, prev_instruction_type);
		}
	}
	if (debug) std::cout <<  "XOR [" << prev_il_instruction->candidate_datatypes.size() << "," << il_operand->candidate_datatypes.size() << "] ==> "  << symbol->candidate_datatypes.size() << " result.\n";
	return NULL;
}

void *fill_candidate_datatypes_c::visit(ANDN_operator_c *symbol) {
	symbol_c *prev_instruction_type, *operand_type;

	if (NULL == prev_il_instruction) return NULL;
	for (unsigned int i = 0; i < prev_il_instruction->candidate_datatypes.size(); i++) {
		for(unsigned int j = 0; j < il_operand->candidate_datatypes.size(); j++) {
			prev_instruction_type = prev_il_instruction->candidate_datatypes[i];
			operand_type = il_operand->candidate_datatypes[j];
			if (is_type_equal(prev_instruction_type, operand_type) &&
					is_ANY_BIT_compatible(operand_type))
				add_datatype_to_candidate_list(symbol, prev_instruction_type);
		}
	}
	if (debug) std::cout <<  "ANDN [" << prev_il_instruction->candidate_datatypes.size() << "," << il_operand->candidate_datatypes.size() << "] ==> "  << symbol->candidate_datatypes.size() << " result.\n";
	return NULL;
}

void *fill_candidate_datatypes_c::visit(ORN_operator_c *symbol) {
	symbol_c *prev_instruction_type, *operand_type;

	if (NULL == prev_il_instruction) return NULL;
	for (unsigned int i = 0; i < prev_il_instruction->candidate_datatypes.size(); i++) {
		for(unsigned int j = 0; j < il_operand->candidate_datatypes.size(); j++) {
			prev_instruction_type = prev_il_instruction->candidate_datatypes[i];
			operand_type = il_operand->candidate_datatypes[j];
			if (is_type_equal(prev_instruction_type, operand_type) &&
					is_ANY_BIT_compatible(operand_type))
				add_datatype_to_candidate_list(symbol, prev_instruction_type);
		}
	}
	if (debug) std::cout <<  "ORN [" << prev_il_instruction->candidate_datatypes.size() << "," << il_operand->candidate_datatypes.size() << "] ==> "  << symbol->candidate_datatypes.size() << " result.\n";
	return NULL;
}

void *fill_candidate_datatypes_c::visit(XORN_operator_c *symbol) {
	symbol_c *prev_instruction_type, *operand_type;

	if (NULL == prev_il_instruction) return NULL;
	for (unsigned int i = 0; i < prev_il_instruction->candidate_datatypes.size(); i++) {
		for(unsigned int j = 0; j < il_operand->candidate_datatypes.size(); j++) {
			prev_instruction_type = prev_il_instruction->candidate_datatypes[i];
			operand_type = il_operand->candidate_datatypes[j];
			if (is_type_equal(prev_instruction_type, operand_type) &&
					is_ANY_BIT_compatible(operand_type))
				add_datatype_to_candidate_list(symbol, prev_instruction_type);
		}
	}
	if (debug) std::cout <<  "XORN [" << prev_il_instruction->candidate_datatypes.size() << "," << il_operand->candidate_datatypes.size() << "] ==> "  << symbol->candidate_datatypes.size() << " result.\n";
	return NULL;
}

void *fill_candidate_datatypes_c::visit(ADD_operator_c *symbol) {
	symbol_c *prev_instruction_type, *operand_type;

	if (NULL == prev_il_instruction) return NULL;
	for(unsigned int i = 0; i < prev_il_instruction->candidate_datatypes.size(); i++) {
		for(unsigned int j = 0; j < il_operand->candidate_datatypes.size(); j++) {
			prev_instruction_type = prev_il_instruction->candidate_datatypes[i];
			operand_type = il_operand->candidate_datatypes[j];
			if (is_type_equal(prev_instruction_type, operand_type) &&
					is_ANY_NUM_compatible(prev_instruction_type))
				add_datatype_to_candidate_list(symbol, prev_instruction_type);
			else {
				symbol_c *result = widening_conversion(prev_instruction_type, operand_type, widen_ADD_table);
				if (result)
					add_datatype_to_candidate_list(symbol, result);

			}
		}
	}
	if (debug) std::cout <<  "ADD [" << prev_il_instruction->candidate_datatypes.size() << "," << il_operand->candidate_datatypes.size() << "] ==> "  << symbol->candidate_datatypes.size() << " result.\n";
	return NULL;
}

void *fill_candidate_datatypes_c::visit(SUB_operator_c *symbol) {
	symbol_c *prev_instruction_type, *operand_type;

	if (NULL == prev_il_instruction) return NULL;
	for(unsigned int i = 0; i < prev_il_instruction->candidate_datatypes.size(); i++) {
		for(unsigned int j = 0; j < il_operand->candidate_datatypes.size(); j++) {
			prev_instruction_type = prev_il_instruction->candidate_datatypes[i];
			operand_type = il_operand->candidate_datatypes[j];
			if (is_type_equal(prev_instruction_type, operand_type) &&
					is_ANY_NUM_compatible(prev_instruction_type))
				add_datatype_to_candidate_list(symbol, prev_instruction_type);
			else {
				symbol_c *result = widening_conversion(prev_instruction_type, operand_type, widen_SUB_table);
				if (result)
					add_datatype_to_candidate_list(symbol, result);
			}
		}
	}
	if (debug) std::cout <<  "SUB [" << prev_il_instruction->candidate_datatypes.size() << "," << il_operand->candidate_datatypes.size() << "] ==> "  << symbol->candidate_datatypes.size() << " result.\n";
	return NULL;
}

void *fill_candidate_datatypes_c::visit(MUL_operator_c *symbol) {
	symbol_c *prev_instruction_type, *operand_type;

	if (NULL == prev_il_instruction) return NULL;
	for(unsigned int i = 0; i < prev_il_instruction->candidate_datatypes.size(); i++) {
		for(unsigned int j = 0; j < il_operand->candidate_datatypes.size(); j++) {
			prev_instruction_type = prev_il_instruction->candidate_datatypes[i];
			operand_type = il_operand->candidate_datatypes[j];
			if (is_type_equal(prev_instruction_type, operand_type) &&
					is_ANY_NUM_compatible(prev_instruction_type))
				add_datatype_to_candidate_list(symbol, prev_instruction_type);
			else {
				symbol_c *result = widening_conversion(prev_instruction_type, operand_type, widen_MUL_table);
				if (result)
					add_datatype_to_candidate_list(symbol, result);
			}
		}
	}
	if (debug) std::cout <<  "MUL [" << prev_il_instruction->candidate_datatypes.size() << "," << il_operand->candidate_datatypes.size() << "] ==> "  << symbol->candidate_datatypes.size() << " result.\n";
	return NULL;
}

void *fill_candidate_datatypes_c::visit(DIV_operator_c *symbol) {
	symbol_c *prev_instruction_type, *operand_type;

	if (NULL == prev_il_instruction) return NULL;
	for(unsigned int i = 0; i < prev_il_instruction->candidate_datatypes.size(); i++) {
		for(unsigned int j = 0; j < il_operand->candidate_datatypes.size(); j++) {
			prev_instruction_type = prev_il_instruction->candidate_datatypes[i];
			operand_type = il_operand->candidate_datatypes[j];
			if (is_type_equal(prev_instruction_type, operand_type) &&
					is_ANY_NUM_compatible(prev_instruction_type))
				add_datatype_to_candidate_list(symbol, prev_instruction_type);
			else {
				symbol_c *result = widening_conversion(prev_instruction_type, operand_type, widen_DIV_table);
				if (result)
					add_datatype_to_candidate_list(symbol, result);
			}
		}
	}
	if (debug) std::cout <<  "DIV [" << prev_il_instruction->candidate_datatypes.size() << "," << il_operand->candidate_datatypes.size() << "] ==> "  << symbol->candidate_datatypes.size() << " result.\n";
	return NULL;
}

void *fill_candidate_datatypes_c::visit(MOD_operator_c *symbol) {
	symbol_c *prev_instruction_type, *operand_type;

	if (NULL == prev_il_instruction) return NULL;
	for(unsigned int i = 0; i < prev_il_instruction->candidate_datatypes.size(); i++) {
		for(unsigned int j = 0; j < il_operand->candidate_datatypes.size(); j++) {
			prev_instruction_type = prev_il_instruction->candidate_datatypes[i];
			operand_type = il_operand->candidate_datatypes[j];
			if (is_type_equal(prev_instruction_type, operand_type) &&
					is_ANY_INT_compatible(prev_instruction_type))
				add_datatype_to_candidate_list(symbol, prev_instruction_type);
		}
	}
	if (debug) std::cout <<  "MOD [" << prev_il_instruction->candidate_datatypes.size() << "," << il_operand->candidate_datatypes.size() << "] ==> "  << symbol->candidate_datatypes.size() << " result.\n";
	return NULL;
}

void *fill_candidate_datatypes_c::visit(GT_operator_c *symbol) {
	bool found = false;

	if (NULL == prev_il_instruction) return NULL;
	for(unsigned int i = 0; i < prev_il_instruction->candidate_datatypes.size(); i++) {
		for(unsigned int j = 0; j < il_operand->candidate_datatypes.size(); j++) {
			if (is_type_equal(prev_il_instruction->candidate_datatypes[i], il_operand->candidate_datatypes[j])
					&& is_ANY_ELEMENTARY_compatible(prev_il_instruction->candidate_datatypes[i])) {
				found = true;
				break;
			}
		}
	}
	if (found) add_datatype_to_candidate_list(symbol, &search_constant_type_c::bool_type_name);
	return NULL;
}

void *fill_candidate_datatypes_c::visit(GE_operator_c *symbol) {
	bool found = false;

	if (NULL == prev_il_instruction) return NULL;
	for(unsigned int i = 0; i < prev_il_instruction->candidate_datatypes.size(); i++) {
		for(unsigned int j = 0; j < il_operand->candidate_datatypes.size(); j++) {
			if (is_type_equal(prev_il_instruction->candidate_datatypes[i], il_operand->candidate_datatypes[j])
					&& is_ANY_ELEMENTARY_compatible(prev_il_instruction->candidate_datatypes[i])) {
				found = true;
				break;
			}
		}
	}
	if (found) add_datatype_to_candidate_list(symbol, &search_constant_type_c::bool_type_name);
	return NULL;
}

void *fill_candidate_datatypes_c::visit(EQ_operator_c *symbol) {
	bool found = false;

	if (NULL == prev_il_instruction) return NULL;
	for(unsigned int i = 0; i < prev_il_instruction->candidate_datatypes.size(); i++) {
		for(unsigned int j = 0; j < il_operand->candidate_datatypes.size(); j++) {
			if (is_type_equal(prev_il_instruction->candidate_datatypes[i], il_operand->candidate_datatypes[j])
					&& is_ANY_ELEMENTARY_compatible(prev_il_instruction->candidate_datatypes[i])) {
				found = true;
				break;
			}
		}
	}
	if (found) add_datatype_to_candidate_list(symbol, &search_constant_type_c::bool_type_name);
	return NULL;
}

void *fill_candidate_datatypes_c::visit(LT_operator_c *symbol) {
	bool found = false;

	if (NULL == prev_il_instruction) return NULL;
	for(unsigned int i = 0; i < prev_il_instruction->candidate_datatypes.size(); i++) {
		for(unsigned int j = 0; j < il_operand->candidate_datatypes.size(); j++) {
			if (is_type_equal(prev_il_instruction->candidate_datatypes[i], il_operand->candidate_datatypes[j])
					&& is_ANY_ELEMENTARY_compatible(prev_il_instruction->candidate_datatypes[i])) {
				found = true;
				break;
			}
		}
	}
	if (found) add_datatype_to_candidate_list(symbol, &search_constant_type_c::bool_type_name);
	return NULL;
}

void *fill_candidate_datatypes_c::visit(LE_operator_c *symbol) {
	bool found = false;

	if (NULL == prev_il_instruction) return NULL;
	for(unsigned int i = 0; i < prev_il_instruction->candidate_datatypes.size(); i++) {
		for(unsigned int j = 0; j < il_operand->candidate_datatypes.size(); j++) {
			if (is_type_equal(prev_il_instruction->candidate_datatypes[i], il_operand->candidate_datatypes[j])
					&& is_ANY_ELEMENTARY_compatible(prev_il_instruction->candidate_datatypes[i])) {
				found = true;
				break;
			}
		}
	}
	if (found) add_datatype_to_candidate_list(symbol, &search_constant_type_c::bool_type_name);
	return NULL;
}

void *fill_candidate_datatypes_c::visit(NE_operator_c *symbol) {
	bool found = false;

	if (NULL == prev_il_instruction) return NULL;
	for(unsigned int i = 0; i < prev_il_instruction->candidate_datatypes.size(); i++) {
		for(unsigned int j = 0; j < il_operand->candidate_datatypes.size(); j++) {
			if (is_type_equal(prev_il_instruction->candidate_datatypes[i], il_operand->candidate_datatypes[j])
					&& is_ANY_ELEMENTARY_compatible(prev_il_instruction->candidate_datatypes[i])) {
				found = true;
				break;
			}
		}
	}
	if (found) add_datatype_to_candidate_list(symbol, &search_constant_type_c::bool_type_name);
	return NULL;
}

void *fill_candidate_datatypes_c::visit(CAL_operator_c *symbol) {
	if (NULL == prev_il_instruction) return NULL;
	for (unsigned int i = 0; i < prev_il_instruction->candidate_datatypes.size(); i++) {
	        /* does not need to be bool type !! */
		add_datatype_to_candidate_list(symbol, prev_il_instruction->candidate_datatypes[i]);
	}
	if (debug) std::cout <<  "CAL [" << prev_il_instruction->candidate_datatypes.size() << "] ==> "  << symbol->candidate_datatypes.size() << " result.\n";
	return NULL;
}

void *fill_candidate_datatypes_c::visit(CALC_operator_c *symbol) {
	if (NULL == prev_il_instruction) return NULL;
	for (unsigned int i = 0; i < prev_il_instruction->candidate_datatypes.size(); i++) {
		if (is_ANY_BOOL_compatible(prev_il_instruction->candidate_datatypes[i]))
			add_datatype_to_candidate_list(symbol, prev_il_instruction->candidate_datatypes[i]);
	}
	if (debug) std::cout <<  "CALC [" << prev_il_instruction->candidate_datatypes.size() << "] ==> "  << symbol->candidate_datatypes.size() << " result.\n";
	return NULL;
}

void *fill_candidate_datatypes_c::visit(CALCN_operator_c *symbol) {
	if (NULL == prev_il_instruction) return NULL;
	for (unsigned int i = 0; i < prev_il_instruction->candidate_datatypes.size(); i++) {
		if (is_ANY_BOOL_compatible(prev_il_instruction->candidate_datatypes[i]))
			add_datatype_to_candidate_list(symbol, prev_il_instruction->candidate_datatypes[i]);
	}
	if (debug) std::cout <<  "CALCN [" << prev_il_instruction->candidate_datatypes.size() << "] ==> "  << symbol->candidate_datatypes.size() << " result.\n";
	return NULL;
}

void *fill_candidate_datatypes_c::visit(RET_operator_c *symbol) {
	if (NULL == prev_il_instruction) return NULL;
	for (unsigned int i = 0; i < prev_il_instruction->candidate_datatypes.size(); i++) {
	        /* does not need to be bool type !! */
		add_datatype_to_candidate_list(symbol, prev_il_instruction->candidate_datatypes[i]);
	}
	if (debug) std::cout <<  "RET [" << prev_il_instruction->candidate_datatypes.size() << "] ==> "  << symbol->candidate_datatypes.size() << " result.\n";
	return NULL;
}

void *fill_candidate_datatypes_c::visit(RETC_operator_c *symbol) {
	if (NULL == prev_il_instruction) return NULL;
	for (unsigned int i = 0; i < prev_il_instruction->candidate_datatypes.size(); i++) {
		if (is_ANY_BOOL_compatible(prev_il_instruction->candidate_datatypes[i]))
			add_datatype_to_candidate_list(symbol, prev_il_instruction->candidate_datatypes[i]);
	}
	if (debug) std::cout <<  "RETC [" << prev_il_instruction->candidate_datatypes.size() << "] ==> "  << symbol->candidate_datatypes.size() << " result.\n";
	return NULL;
}

void *fill_candidate_datatypes_c::visit(RETCN_operator_c *symbol) {
	if (NULL == prev_il_instruction) return NULL;
	for (unsigned int i = 0; i < prev_il_instruction->candidate_datatypes.size(); i++) {
		if (is_ANY_BOOL_compatible(prev_il_instruction->candidate_datatypes[i]))
			add_datatype_to_candidate_list(symbol, prev_il_instruction->candidate_datatypes[i]);
	}
	if (debug) std::cout <<  "RETCN [" << prev_il_instruction->candidate_datatypes.size() << "] ==> "  << symbol->candidate_datatypes.size() << " result.\n";
	return NULL;
}

void *fill_candidate_datatypes_c::visit(JMP_operator_c *symbol) {
	if (NULL == prev_il_instruction) return NULL;
	for (unsigned int i = 0; i < prev_il_instruction->candidate_datatypes.size(); i++) {
	        /* does not need to be bool type !! */
		add_datatype_to_candidate_list(symbol, prev_il_instruction->candidate_datatypes[i]);
	}
	if (debug) std::cout <<  "JMP [" << prev_il_instruction->candidate_datatypes.size() << "] ==> "  << symbol->candidate_datatypes.size() << " result.\n";
	return NULL;
}

void *fill_candidate_datatypes_c::visit(JMPC_operator_c *symbol) {
	for (unsigned int i = 0; i < prev_il_instruction->candidate_datatypes.size(); i++) {
		if (is_ANY_BOOL_compatible(prev_il_instruction->candidate_datatypes[i]))
			add_datatype_to_candidate_list(symbol, prev_il_instruction->candidate_datatypes[i]);
	}
	if (debug) std::cout <<  "JMPC [" << prev_il_instruction->candidate_datatypes.size() << "] ==> "  << symbol->candidate_datatypes.size() << " result.\n";
	return NULL;
}

void *fill_candidate_datatypes_c::visit(JMPCN_operator_c *symbol) {
	for (unsigned int i = 0; i < prev_il_instruction->candidate_datatypes.size(); i++) {
		if (is_ANY_BOOL_compatible(prev_il_instruction->candidate_datatypes[i]))
			add_datatype_to_candidate_list(symbol, prev_il_instruction->candidate_datatypes[i]);
	}
	if (debug) std::cout <<  "JMPCN [" << prev_il_instruction->candidate_datatypes.size() << "] ==> "  << symbol->candidate_datatypes.size() << " result.\n";
	return NULL;
}
/* Symbol class handled together with function call checks */
// void *visit(il_assign_operator_c *symbol, variable_name);
/* Symbol class handled together with function call checks */
// void *visit(il_assign_operator_c *symbol, option, variable_name);

/***************************************/
/* B.3 - Language ST (Structured Text) */
/***************************************/
/***********************/
/* B 3.1 - Expressions */
/***********************/

void *fill_candidate_datatypes_c::visit(or_expression_c *symbol) {
	symbol->l_exp->accept(*this);
	symbol->r_exp->accept(*this);
	for (unsigned  int i = 0; i < symbol->l_exp->candidate_datatypes.size(); i++) {
		for (unsigned  int j = 0; j < symbol->r_exp->candidate_datatypes.size(); j++) {
			if (is_type_equal(symbol->l_exp->candidate_datatypes[i], symbol->r_exp->candidate_datatypes[j])
					&& is_ANY_BIT_compatible(symbol->l_exp->candidate_datatypes[i]))
				add_datatype_to_candidate_list(symbol, symbol->l_exp->candidate_datatypes[i]);
		}
	}
	return NULL;
}


void *fill_candidate_datatypes_c::visit(xor_expression_c *symbol) {
	symbol->l_exp->accept(*this);
	symbol->r_exp->accept(*this);

	for (unsigned  int i = 0; i < symbol->l_exp->candidate_datatypes.size(); i++) {
		for (unsigned  int j = 0; j < symbol->r_exp->candidate_datatypes.size(); j++) {
			if (is_type_equal(symbol->l_exp->candidate_datatypes[i], symbol->r_exp->candidate_datatypes[j])
					&& is_ANY_BIT_compatible(symbol->l_exp->candidate_datatypes[i]))
				add_datatype_to_candidate_list(symbol, symbol->l_exp->candidate_datatypes[i]);
		}
	}
	return NULL;
}


void *fill_candidate_datatypes_c::visit(and_expression_c *symbol) {
	symbol->l_exp->accept(*this);
	symbol->r_exp->accept(*this);

	for (unsigned  int i = 0; i < symbol->l_exp->candidate_datatypes.size(); i++) {
		for (unsigned int j = 0; j < symbol->r_exp->candidate_datatypes.size(); j++) {
			if (is_type_equal(symbol->l_exp->candidate_datatypes[i], symbol->r_exp->candidate_datatypes[j])
					&& is_ANY_BIT_compatible(symbol->l_exp->candidate_datatypes[i]))
				add_datatype_to_candidate_list(symbol, symbol->l_exp->candidate_datatypes[i]);
		}
	}
	return NULL;
}


void *fill_candidate_datatypes_c::visit(equ_expression_c *symbol) {
	symbol->l_exp->accept(*this);
	symbol->r_exp->accept(*this);
	bool found = false;

	for (unsigned int i = 0; i < symbol->l_exp->candidate_datatypes.size(); i++) {
		for (unsigned int j = 0; j < symbol->r_exp->candidate_datatypes.size(); j++) {
			if (is_type_equal(symbol->l_exp->candidate_datatypes[i], symbol->r_exp->candidate_datatypes[j])
					&& is_ANY_ELEMENTARY_compatible(symbol->l_exp->candidate_datatypes[i])) {
				found = true;
				break;
			}
		}
	}
	if (found) add_datatype_to_candidate_list(symbol, &search_constant_type_c::bool_type_name);
	return NULL;
}


void *fill_candidate_datatypes_c::visit(notequ_expression_c *symbol)  {
	symbol->l_exp->accept(*this);
	symbol->r_exp->accept(*this);
	bool found = false;

	for (unsigned int i = 0; i < symbol->l_exp->candidate_datatypes.size(); i++) {
		for (unsigned int j = 0; j < symbol->r_exp->candidate_datatypes.size(); j++) {
			if (is_type_equal(symbol->l_exp->candidate_datatypes[i], symbol->r_exp->candidate_datatypes[j])
					&& is_ANY_ELEMENTARY_compatible(symbol->l_exp->candidate_datatypes[i])) {
				found = true;
				break;
			}
		}
	}
	if (found)
		add_datatype_to_candidate_list(symbol, &search_constant_type_c::bool_type_name);
	return NULL;
}


void *fill_candidate_datatypes_c::visit(lt_expression_c *symbol) {
	symbol->l_exp->accept(*this);
	symbol->r_exp->accept(*this);
	bool found = false;

	for (unsigned int i = 0; i < symbol->l_exp->candidate_datatypes.size(); i++) {
		for (unsigned int j = 0; j < symbol->r_exp->candidate_datatypes.size(); j++) {
			if (is_type_equal(symbol->l_exp->candidate_datatypes[i], symbol->r_exp->candidate_datatypes[j])
					&& is_ANY_ELEMENTARY_compatible(symbol->l_exp->candidate_datatypes[i])) {
				found = true;
				break;
			}
		}
	}
	if (found)
		add_datatype_to_candidate_list(symbol, &search_constant_type_c::bool_type_name);
	return NULL;
}


void *fill_candidate_datatypes_c::visit(gt_expression_c *symbol) {
	symbol->l_exp->accept(*this);
	symbol->r_exp->accept(*this);
	bool found = false;

	for (unsigned int i = 0; i < symbol->l_exp->candidate_datatypes.size(); i++) {
		for (unsigned int j = 0; j < symbol->r_exp->candidate_datatypes.size(); j++) {
			if (is_type_equal(symbol->l_exp->candidate_datatypes[i], symbol->r_exp->candidate_datatypes[j])
					&& is_ANY_ELEMENTARY_compatible(symbol->l_exp->candidate_datatypes[i])) {
				found = true;
				break;
			}
		}
	}
	if (found)
		add_datatype_to_candidate_list(symbol, &search_constant_type_c::bool_type_name);
	return NULL;
}

void *fill_candidate_datatypes_c::visit(le_expression_c *symbol) {
	symbol->l_exp->accept(*this);
	symbol->r_exp->accept(*this);
	bool found = false;

	for (unsigned int i = 0; i < symbol->l_exp->candidate_datatypes.size(); i++) {
		for (unsigned int j = 0; j < symbol->r_exp->candidate_datatypes.size(); j++) {
			if (is_type_equal(symbol->l_exp->candidate_datatypes[i], symbol->r_exp->candidate_datatypes[j])
					&& is_ANY_ELEMENTARY_compatible(symbol->l_exp->candidate_datatypes[i])) {
				found = true;
				break;
			}
		}
	}
	if (found)
		add_datatype_to_candidate_list(symbol, &search_constant_type_c::bool_type_name);
	return NULL;
}

void *fill_candidate_datatypes_c::visit(ge_expression_c *symbol) {
	symbol->l_exp->accept(*this);
	symbol->r_exp->accept(*this);
	bool found = false;

	for (unsigned int i = 0; i < symbol->l_exp->candidate_datatypes.size(); i++) {
		for (unsigned int j = 0; j < symbol->r_exp->candidate_datatypes.size(); j++) {
			if (is_type_equal(symbol->l_exp->candidate_datatypes[i], symbol->r_exp->candidate_datatypes[j])
					&& is_ANY_ELEMENTARY_compatible(symbol->l_exp->candidate_datatypes[i])) {
				found = true;
				break;
			}
		}
	}
	if (found)
		add_datatype_to_candidate_list(symbol, &search_constant_type_c::bool_type_name);
	return NULL;
}

void *fill_candidate_datatypes_c::visit(add_expression_c *symbol) {
	/* The following code is correct when handling the addition of 2 symbolic_variables
	 * In this case, adding two variables (e.g. USINT_var1 + USINT_var2) will always yield
	 * the same data type, even if the result of the adition could not fit inside the same
	 * data type (due to overflowing)
	 *
	 * However, when adding two literals (e.g. USINT#42 + USINT#3)
	 * we should be able to detect overflows of the result, and therefore not consider
	 * that the result may be of type USINT.
	 * Currently we do not yet detect these overflows, and allow handling the sum of two USINTs
	 * as always resulting in an USINT, even in the following expression
	 * (USINT#65535 + USINT#2).
	 *
	 * In the future we can add some code to reduce
	 * all the expressions that are based on literals into the resulting literal
	 * value (maybe some visitor class that will run before or after data type
	 * checking). Since this class will have to be very careful to make sure it implements the same mathematical
	 * details (e.g. how to round and truncate numbers) as defined in IEC 61131-3, we will leave this to the future.
	 * Also, the question will arise if we should also replace calls to standard
	 * functions if the input parameters are all literals (e.g. ADD(42, 42)). This
	 * means this class will be more difficult than it appears at first.
	 */
	symbol_c *left_type, *right_type;

	symbol->l_exp->accept(*this);
	symbol->r_exp->accept(*this);
	for(unsigned int i = 0; i < symbol->l_exp->candidate_datatypes.size(); i++) {
		for(unsigned int j = 0; j < symbol->r_exp->candidate_datatypes.size(); j++) {
			left_type = symbol->l_exp->candidate_datatypes[i];
			right_type = symbol->r_exp->candidate_datatypes[j];
			if (is_type_equal(left_type, right_type) && is_ANY_NUM_compatible(left_type))
				add_datatype_to_candidate_list(symbol, left_type);
			else {
				symbol_c *result = widening_conversion(left_type, right_type, widen_ADD_table);
				if (result)
					add_datatype_to_candidate_list(symbol, result);
			}
		}
	}
	if (debug) std::cout <<  "+ [" << symbol->l_exp->candidate_datatypes.size() << "," << symbol->r_exp->candidate_datatypes.size() << "] ==> "  << symbol->candidate_datatypes.size() << " result.\n";
	return NULL;
}


void *fill_candidate_datatypes_c::visit(sub_expression_c *symbol) {
	symbol_c *left_type, *right_type;

	symbol->l_exp->accept(*this);
	symbol->r_exp->accept(*this);
	for(unsigned int i = 0; i < symbol->l_exp->candidate_datatypes.size(); i++) {
		for(unsigned int j = 0; j < symbol->r_exp->candidate_datatypes.size(); j++) {
			left_type = symbol->l_exp->candidate_datatypes[i];
			right_type = symbol->r_exp->candidate_datatypes[j];
			if (is_type_equal(left_type, right_type) && is_ANY_NUM_compatible(left_type))
				add_datatype_to_candidate_list(symbol, left_type);
			else {
				symbol_c *result = widening_conversion(left_type, right_type, widen_SUB_table);
				if (result)
					add_datatype_to_candidate_list(symbol, result);
			}
		}
	}
	if (debug) std::cout <<  "- [" << symbol->l_exp->candidate_datatypes.size() << "," << symbol->r_exp->candidate_datatypes.size() << "] ==> "  << symbol->candidate_datatypes.size() << " result.\n";
	return NULL;
}


void *fill_candidate_datatypes_c::visit(mul_expression_c *symbol) {
	symbol_c *left_type, *right_type;

	symbol->l_exp->accept(*this);
	symbol->r_exp->accept(*this);
	for(unsigned int i = 0; i < symbol->l_exp->candidate_datatypes.size(); i++) {
		for(unsigned int j = 0; j < symbol->r_exp->candidate_datatypes.size(); j++) {
			left_type = symbol->l_exp->candidate_datatypes[i];
			right_type = symbol->r_exp->candidate_datatypes[j];
			if      (is_type_equal(left_type, right_type) && is_ANY_NUM_compatible(left_type))
				add_datatype_to_candidate_list(symbol, left_type);
			else {
				symbol_c *result = widening_conversion(left_type, right_type, widen_MUL_table);
				if (result)
					add_datatype_to_candidate_list(symbol, result);
			}

		}
	}
	if (debug) std::cout << "* [" << symbol->l_exp->candidate_datatypes.size() << "," << symbol->r_exp->candidate_datatypes.size() << "] ==> "  << symbol->candidate_datatypes.size() << " result.\n";

	return NULL;
}

void *fill_candidate_datatypes_c::visit(div_expression_c *symbol) {
	symbol_c *left_type, *right_type;

	symbol->l_exp->accept(*this);
	symbol->r_exp->accept(*this);
	for(unsigned int i = 0; i < symbol->l_exp->candidate_datatypes.size(); i++) {
		for(unsigned int j = 0; j < symbol->r_exp->candidate_datatypes.size(); j++) {
			left_type = symbol->l_exp->candidate_datatypes[i];
			right_type = symbol->r_exp->candidate_datatypes[j];
			if      (is_type_equal(left_type, right_type) && is_ANY_NUM_type(left_type))
				add_datatype_to_candidate_list(symbol, left_type);
			else {
				symbol_c *result = widening_conversion(left_type, right_type, widen_DIV_table);
				if (result)
					add_datatype_to_candidate_list(symbol, result);
			}

		}
	}
	if (debug) std::cout << "/ [" << symbol->l_exp->candidate_datatypes.size() << "," << symbol->r_exp->candidate_datatypes.size() << "] ==> "  << symbol->candidate_datatypes.size() << " result.\n";
	return NULL;
}


void *fill_candidate_datatypes_c::visit(mod_expression_c *symbol) {
	symbol_c *left_type, *right_type;

	symbol->l_exp->accept(*this);
	symbol->r_exp->accept(*this);
	for (unsigned int i = 0; i < symbol->l_exp->candidate_datatypes.size(); i++) {
		for(unsigned int j = 0; j < symbol->r_exp->candidate_datatypes.size(); j++) {
			left_type = symbol->l_exp->candidate_datatypes[i];
			right_type = symbol->r_exp->candidate_datatypes[j];
			if (is_type_equal(left_type, right_type) && is_ANY_INT_compatible(left_type))
				add_datatype_to_candidate_list(symbol, left_type);
		}
	}
	if (debug) std::cout << "mod [" << symbol->l_exp->candidate_datatypes.size() << "," << symbol->r_exp->candidate_datatypes.size() << "] ==> "  << symbol->candidate_datatypes.size() << " result.\n";
	return NULL;
}


void *fill_candidate_datatypes_c::visit(power_expression_c *symbol) {
	symbol_c *left_type, *right_type;
	bool check_ok;

	symbol->l_exp->accept(*this);
	symbol->r_exp->accept(*this);
	check_ok = false;
	for (unsigned int i = 0; i < symbol->l_exp->candidate_datatypes.size(); i++) {
		left_type = symbol->l_exp->candidate_datatypes[i];
		if (is_ANY_REAL_compatible(left_type)) {
			check_ok = true;
			break;
		}
	}
	if (! check_ok) return NULL;
	check_ok = false;
	for(unsigned int j = 0; j < symbol->r_exp->candidate_datatypes.size(); j++) {
		right_type = symbol->r_exp->candidate_datatypes[j];
		if (is_ANY_NUM_compatible(right_type)) {
			check_ok = true;
			break;
		}
	}
	if (! check_ok) return NULL;
	for (unsigned int i = 0; i < symbol->l_exp->candidate_datatypes.size(); i++) {
		add_datatype_to_candidate_list(symbol, symbol->l_exp->candidate_datatypes[i]);
	}
	if (debug) std::cout << "** [" << symbol->l_exp->candidate_datatypes.size() << "," << symbol->r_exp->candidate_datatypes.size() << "] ==> "  << symbol->candidate_datatypes.size() << " result.\n";
	return NULL;
}


void *fill_candidate_datatypes_c::visit(neg_expression_c *symbol) {
  /* NOTE: The standard defines the syntax for this 'negation' operation, but
   *       does not define the its semantics.
   *
   *       We could be tempted to consider that the semantics of the
   *       'negation' operation are similar/identical to the semantics of the 
   *       SUB expression/operation. This would include assuming that the
   *       possible datatypes for the 'negation' operation is also
   *       the same as those for the SUB expression/operation, namely ANY_MAGNITUDE.
   *
   *       However, this would then mean that the following ST code would be 
   *       syntactically and semantically correct:
   *       uint_var := - (uint_var);
   *
   *       According to the standard, the above code should result in a 
   *       runtime error, when we try to apply a negative value to the
   *       UINT typed variable 'uint_var'.
   *
   *       It is much easier for the compiler to detect this at compile time,
   *       and it is probably safer to the resulting code too.
   *
   *       To detect these tyes of errors at compile time, the easisest solution
   *       is to only allow ANY_NUM datatytpes that are signed.
   *        So, that is what we do here!
   */
	symbol->exp->accept(*this);
	for (unsigned int i = 0; i < symbol->exp->candidate_datatypes.size(); i++) {
		if (is_ANY_signed_MAGNITUDE_compatible(symbol->exp->candidate_datatypes[i]))
			add_datatype_to_candidate_list(symbol, symbol->exp->candidate_datatypes[i]);
	}
	if (debug) std::cout << "neg [" << symbol->exp->candidate_datatypes.size() << "] ==> "  << symbol->candidate_datatypes.size() << " result.\n";
	return NULL;
}


void *fill_candidate_datatypes_c::visit(not_expression_c *symbol) {
	symbol->exp->accept(*this);
	for (unsigned int i = 0; i < symbol->exp->candidate_datatypes.size(); i++) {
		if      (is_ANY_BIT_compatible(symbol->exp->candidate_datatypes[i]))
			add_datatype_to_candidate_list(symbol, symbol->exp->candidate_datatypes[i]);
	}
	if (debug) std::cout << "not [" << symbol->exp->candidate_datatypes.size() << "] ==> "  << symbol->candidate_datatypes.size() << " result.\n";
	return NULL;
}


void *fill_candidate_datatypes_c::visit(function_invocation_c *symbol) {
	if      (NULL != symbol->formal_param_list)        symbol->   formal_param_list->accept(*this);
	else if (NULL != symbol->nonformal_param_list)     symbol->nonformal_param_list->accept(*this);
	else ERROR;

	generic_function_call_t fcall_param = {
		/* fcall_param.function_name               = */ symbol->function_name,
		/* fcall_param.nonformal_operand_list      = */ symbol->nonformal_param_list,
		/* fcall_param.formal_operand_list         = */ symbol->formal_param_list,
		/* enum {POU_FB, POU_function} POU_type    = */ generic_function_call_t::POU_function,
		/* fcall_param.candidate_functions         = */ symbol->candidate_functions,
		/* fcall_param.called_function_declaration = */ symbol->called_function_declaration,
		/* fcall_param.extensible_param_count      = */ symbol->extensible_param_count
	};
	handle_function_call(symbol, fcall_param);

	if (debug) std::cout << "function_invocation_c [" << symbol->candidate_datatypes.size() << "] result.\n";
	return NULL;
}



/********************/
/* B 3.2 Statements */
/********************/
// SYM_LIST(statement_list_c)
/* The visitor of the base class search_visitor_c will handle calling each instruction in the list.
 * We do not need to do anything here...
 */
// void *fill_candidate_datatypes_c::visit(statement_list_c *symbol)


/*********************************/
/* B 3.2.1 Assignment Statements */
/*********************************/
void *fill_candidate_datatypes_c::visit(assignment_statement_c *symbol) {
	symbol_c *left_type, *right_type;

	symbol->l_exp->accept(*this);
	symbol->r_exp->accept(*this);
	for (unsigned int i = 0; i < symbol->l_exp->candidate_datatypes.size(); i++) {
		for(unsigned int j = 0; j < symbol->r_exp->candidate_datatypes.size(); j++) {
			left_type = symbol->l_exp->candidate_datatypes[i];
			right_type = symbol->r_exp->candidate_datatypes[j];
			if (is_type_equal(left_type, right_type))
				add_datatype_to_candidate_list(symbol, left_type);
		}
	}
	if (debug) std::cout << ":= [" << symbol->l_exp->candidate_datatypes.size() << "," << symbol->r_exp->candidate_datatypes.size() << "] ==> "  << symbol->candidate_datatypes.size() << " result.\n";
	return NULL;
}

/*****************************************/
/* B 3.2.2 Subprogram Control Statements */
/*****************************************/
void *fill_candidate_datatypes_c::visit(fb_invocation_c *symbol) {
	symbol_c *fb_type_id = search_varfb_instance_type->get_basetype_id(symbol->fb_name);
	/* Although a call to a non-declared FB is a semantic error, this is currently caught by stage 2! */
	if (NULL == fb_type_id) ERROR;

	function_block_declaration_c *fb_decl = function_block_type_symtable.find_value(fb_type_id);
	if (function_block_type_symtable.end_value() == fb_decl) 
		/* The fb_name not the name of a FB instance. Most probably it is the name of a variable of some other type. */
		fb_decl = NULL;

	/* Although a call to a non-declared FB is a semantic error, this is currently caught by stage 2! */
	if (NULL == fb_decl) ERROR;
	
	if (symbol->   formal_param_list != NULL) symbol->formal_param_list->accept(*this);
	if (symbol->nonformal_param_list != NULL) symbol->nonformal_param_list->accept(*this);

	/* The print_datatypes_error_c does not rely on this called_fb_declaration pointer being != NULL to conclude that
	 * we have a datat type incompatibility error, so setting it to the correct fb_decl is actually safe,
	 * as the compiler will never reach the compilation stage!
	 */
	symbol->called_fb_declaration = fb_decl;

	if (debug) std::cout << "FB [] ==> "  << symbol->candidate_datatypes.size() << " result.\n";
	return NULL;
}



/********************************/
/* B 3.2.3 Selection Statements */
/********************************/
void *fill_candidate_datatypes_c::visit(if_statement_c *symbol) {
	symbol->expression->accept(*this);
	if (NULL != symbol->statement_list)
		symbol->statement_list->accept(*this);
	if (NULL != symbol->elseif_statement_list)
		symbol->elseif_statement_list->accept(*this);
	if (NULL != symbol->else_statement_list)
		symbol->else_statement_list->accept(*this);
	return NULL;
}


void *fill_candidate_datatypes_c::visit(elseif_statement_c *symbol) {
	symbol->expression->accept(*this);
	if (NULL != symbol->statement_list)
		symbol->statement_list->accept(*this);
	return NULL;
}

/* CASE expression OF case_element_list ELSE statement_list END_CASE */
// SYM_REF3(case_statement_c, expression, case_element_list, statement_list)
void *fill_candidate_datatypes_c::visit(case_statement_c *symbol) {
	symbol->expression->accept(*this);
	if (NULL != symbol->case_element_list)
		symbol->case_element_list->accept(*this);
	if (NULL != symbol->statement_list)
		symbol->statement_list->accept(*this);
	return NULL;
}


/* helper symbol for case_statement */
// SYM_LIST(case_element_list_c)
/* NOTE: visitor method for case_element_list_c is not required since we inherit from iterator_visitor_c */

/*  case_list ':' statement_list */
// SYM_REF2(case_element_c, case_list, statement_list)
/* NOTE: visitor method for case_element_c is not required since we inherit from iterator_visitor_c */

// SYM_LIST(case_list_c)
/* NOTE: visitor method for case_list_c is not required since we inherit from iterator_visitor_c */

/********************************/
/* B 3.2.4 Iteration Statements */
/********************************/

void *fill_candidate_datatypes_c::visit(for_statement_c *symbol) {
	symbol->control_variable->accept(*this);
	symbol->beg_expression->accept(*this);
	symbol->end_expression->accept(*this);
	if (NULL != symbol->by_expression)
		symbol->by_expression->accept(*this);
	if (NULL != symbol->statement_list)
		symbol->statement_list->accept(*this);
	return NULL;
}


void *fill_candidate_datatypes_c::visit(while_statement_c *symbol) {
	symbol->expression->accept(*this);
	if (NULL != symbol->statement_list)
		symbol->statement_list->accept(*this);
	return NULL;
}


void *fill_candidate_datatypes_c::visit(repeat_statement_c *symbol) {
	symbol->expression->accept(*this);
	if (NULL != symbol->statement_list)
		symbol->statement_list->accept(*this);
	return NULL;
}