stage3/visit_expression_type.cc
author Catarina Boucinha <ccb@fe.up.pt>
Thu, 27 Aug 2009 16:29:23 +0100
changeset 204 8ffa211b7f9a
child 210 8387cac2aba6
child 257 90782e241346
permissions -rw-r--r--
Adding missing Stage3 files.
/*
 * (c) 2009 Mario de Sousa
 *
 * Offered to the public under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2 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.
 *
 * 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 IL and ST compiler.
 *
 * Based on the
 * FINAL DRAFT - IEC 61131-3, 2nd Ed. (2001-12-10)
 *
 */


/* Verify whether the semantic rules of data type compatibility are being followed.
 *
 * For example:
 */

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



#define FIRST_(symbol1, symbol2) (((symbol1)->first_line   < (symbol2)->first_line)   ? (symbol1) :    \
                                  ((symbol1)->first_line   > (symbol2)->first_line)   ? (symbol2) :    \
                                  ((symbol1)->first_column < (symbol2)->first_column) ? (symbol1) :    \
                                  ((symbol1)->first_column > (symbol2)->first_column) ? (symbol2) :    \
                                  (symbol1))

#define  LAST_(symbol1, symbol2) (((symbol1)->last_line    < (symbol2)->last_line)    ? (symbol2) :    \
                                  ((symbol1)->last_line    > (symbol2)->last_line)    ? (symbol1) :    \
                                  ((symbol1)->last_column  < (symbol2)->last_column)  ? (symbol2) :    \
                                  ((symbol1)->last_column  > (symbol2)->last_column)  ? (symbol1) :    \
                                  (symbol1))

#define STAGE3_ERROR(symbol1, symbol2, msg) {                                          \
    printf("semantic error between (%d:%d) and (%d:%d): %s\n",                         \
           FIRST_(symbol1,symbol2)->first_line, FIRST_(symbol1,symbol2)->first_column, \
           LAST_(symbol1,symbol2) ->last_line,  LAST_(symbol1,symbol2) ->last_column,  \
           msg);                                                                       \
    il_error = true;                                                                   \
  }





void *visit_expression_type_c::visit(program_declaration_c *symbol) {
  search_varfb_instance_type = new search_varfb_instance_type_c(symbol);
  symbol->var_declarations->accept(*this);
  printf("checking semantics in body of program %s\n", ((token_c *)(symbol->program_type_name))->value);
  il_parenthesis_level = 0;
  il_error = false;
  il_default_variable_type = NULL;
  symbol->function_block_body->accept(*this);
  il_default_variable_type = NULL;
  delete search_varfb_instance_type;
  return NULL;
}

void *visit_expression_type_c::visit(function_declaration_c *symbol) {
  search_varfb_instance_type = new search_varfb_instance_type_c(symbol);
  symbol->var_declarations_list->accept(*this);
  printf("checking semantics in body of function %s\n", ((token_c *)(symbol->derived_function_name))->value);
  il_parenthesis_level = 0;
  il_error = false;
  il_default_variable_type = NULL;
  symbol->function_body->accept(*this);
  il_default_variable_type = NULL;
  delete search_varfb_instance_type;
  return NULL;
}

void *visit_expression_type_c::visit(function_block_declaration_c *symbol) {
  search_varfb_instance_type = new search_varfb_instance_type_c(symbol);
  symbol->var_declarations->accept(*this);
  printf("checking semantics in body of FB %s\n", ((token_c *)(symbol->fblock_name))->value);
  il_parenthesis_level = 0;
  il_error = false;
  il_default_variable_type = NULL;
  symbol->fblock_body->accept(*this);
  il_default_variable_type = NULL;
  delete search_varfb_instance_type;
  return NULL;
}









visit_expression_type_c::visit_expression_type_c(symbol_c *search_scope) {
}

visit_expression_type_c::~visit_expression_type_c(void) {
}


/* A helper function... */
bool visit_expression_type_c::is_ANY_ELEMENTARY_type(symbol_c *type_symbol) {
  if (type_symbol == NULL) {ERROR;}
  return is_ANY_MAGNITUDE_type(type_symbol)
      || is_ANY_BIT_type(type_symbol)
      || is_ANY_STRING_type(type_symbol)
      || is_ANY_DATE_type(type_symbol);
}


/* A helper function... */
bool visit_expression_type_c::is_ANY_MAGNITUDE_type(symbol_c *type_symbol) {
  if (type_symbol == NULL) {ERROR;}
  if (typeid(*type_symbol) == typeid(time_type_name_c)) {return true;}
  return is_ANY_NUM_type(type_symbol);
}


/* A helper function... */
bool visit_expression_type_c::is_ANY_NUM_type(symbol_c *type_symbol) {
  if (type_symbol == NULL) {ERROR;}
  return is_ANY_REAL_type(type_symbol) || is_ANY_INT_type(type_symbol);
}


/* A helper function... */
bool visit_expression_type_c::is_ANY_DATE_type(symbol_c *type_symbol) {
  if (type_symbol == NULL) {ERROR;}
  if (typeid(*type_symbol) == typeid(date_type_name_c)) {return true;}
  if (typeid(*type_symbol) == typeid(tod_type_name_c)) {return true;}
  if (typeid(*type_symbol) == typeid(dt_type_name_c)) {return true;}
  return false;
}


/* A helper function... */
bool visit_expression_type_c::is_ANY_STRING_type(symbol_c *type_symbol) {
  if (type_symbol == NULL) {ERROR;}
  if (typeid(*type_symbol) == typeid(string_type_name_c)) {return true;}
  if (typeid(*type_symbol) == typeid(wstring_type_name_c)) {return true;}
  return false;
}


/* A helper function... */
bool visit_expression_type_c::is_ANY_INT_type(symbol_c *type_symbol) {
  if (type_symbol == NULL) {ERROR;}
  if (typeid(*type_symbol) == typeid(sint_type_name_c))  {return true;}
  if (typeid(*type_symbol) == typeid(int_type_name_c))   {return true;}
  if (typeid(*type_symbol) == typeid(dint_type_name_c))  {return true;}
  if (typeid(*type_symbol) == typeid(lint_type_name_c))  {return true;}
  if (typeid(*type_symbol) == typeid(usint_type_name_c)) {return true;}
  if (typeid(*type_symbol) == typeid(uint_type_name_c))  {return true;}
  if (typeid(*type_symbol) == typeid(udint_type_name_c)) {return true;}
  if (typeid(*type_symbol) == typeid(ulint_type_name_c)) {return true;}
  if (is_literal_integer_type(type_symbol))              {return true;}
  return false;
}


/* A helper function... */
bool visit_expression_type_c::is_ANY_REAL_type(symbol_c *type_symbol) {
  if (type_symbol == NULL) {ERROR;}
  if (typeid(*type_symbol) == typeid(real_type_name_c))  {return true;}
  if (typeid(*type_symbol) == typeid(lreal_type_name_c)) {return true;}
  if (is_literal_real_type(type_symbol))                 {return true;}
  return false;
}


/* A helper function... */
bool visit_expression_type_c::is_ANY_BIT_type(symbol_c *type_symbol) {
  if (type_symbol == NULL) {ERROR;}
  if (typeid(*type_symbol) == typeid(bool_type_name_c))  {return true;}
  if (typeid(*type_symbol) == typeid(byte_type_name_c))  {return true;}
  if (typeid(*type_symbol) == typeid(word_type_name_c))  {return true;}
  if (typeid(*type_symbol) == typeid(dword_type_name_c)) {return true;}
  if (typeid(*type_symbol) == typeid(lword_type_name_c)) {return true;}
  if (is_literal_integer_type(type_symbol))              {return true;}
  return false;
}


/* A helper function... */
bool visit_expression_type_c::is_BOOL_type(symbol_c *type_symbol) {
  if (type_symbol == NULL) {ERROR;}
  if (typeid(*type_symbol) == typeid(bool_type_name_c))  {return true;}
  if (is_literal_bool_type(type_symbol))                 {return true;}
  return false;
}


#define sizeoftype(symbol) get_sizeof_datatype_c::getsize(symbol)


/* A helper function... */
bool visit_expression_type_c::is_literal_integer_type(symbol_c *type_symbol) {
  if (type_symbol == NULL) {return true;}
  if (typeid(*type_symbol) == typeid(integer_c))        {return true;}
  if (typeid(*type_symbol) == typeid(binary_integer_c)) {return true;}
  if (typeid(*type_symbol) == typeid(octal_integer_c))  {return true;}
  if (typeid(*type_symbol) == typeid(hex_integer_c))    {return true;}
  return false;
}


/* A helper function... */
bool visit_expression_type_c::is_literal_real_type(symbol_c *type_symbol) {
  if (type_symbol == NULL) {return true;}
  if (typeid(*type_symbol) == typeid(real_c)) {return true;}
  return false;
}


/* A helper function... */
bool visit_expression_type_c::is_literal_bool_type(symbol_c *type_symbol) {
  bool_type_name_c bool_t;

  if (type_symbol == NULL) {return true;}
  if (typeid(*type_symbol) == typeid(boolean_true_c))    {return true;}
  if (typeid(*type_symbol) == typeid(boolean_false_c))   {return true;}
  if (is_literal_integer_type(type_symbol))
    if (sizeoftype(&bool_t) >= sizeoftype(type_symbol))  {return true;}
  return false;
}


/* Determine the common data type between two data types.
 * If no common data type found, return NULL.
 *
 * If data types are identical, return the first (actually any would do...).
 * If any of the data types is a literal, we confirm that 
 *   the literal uses less bits than the fixed size data type.
 *   e.g. BYTE and 1024 returns NULL
 *        BYTE and 255  returns BYTE
 *
 * If two literals, then return the literal that requires more bits...
 */
symbol_c *visit_expression_type_c::common_type__(symbol_c *first_type, symbol_c *second_type) {
  if (first_type == NULL && second_type == NULL) {ERROR;}
  if (first_type == NULL)  {return second_type;}
  if (second_type == NULL) {return first_type;}

  if (is_literal_integer_type(first_type) && is_literal_integer_type(second_type))
    {return ((sizeoftype(first_type) > sizeoftype(second_type))? first_type:second_type);}

  if (is_literal_real_type(first_type) && is_literal_real_type(second_type))
    {return ((sizeoftype(first_type) > sizeoftype(second_type))? first_type:second_type);}

  if (is_literal_bool_type(first_type) && is_literal_bool_type(second_type))
    {return first_type;}

  /* This check can only be made after the is_literal_XXXX checks */
  /* When two literals of the same type, with identical typeid's are checked,
   * we must return the one that occupies more bits...
   */
  if (typeid(*first_type) == typeid(*second_type)) {return first_type;}

  if (is_BOOL_type(first_type)      && is_literal_bool_type(second_type))     {return first_type;}
  if (is_BOOL_type(second_type)     && is_literal_bool_type(first_type))      {return second_type;}

  if (is_ANY_BIT_type(first_type)     && is_literal_integer_type(second_type))
    {return ((sizeoftype(first_type)  >= sizeoftype(second_type))? first_type :NULL);}
  if (is_ANY_BIT_type(second_type)    && is_literal_integer_type(first_type))
    {return ((sizeoftype(second_type) >= sizeoftype(first_type)) ? second_type:NULL);}

  if (is_ANY_INT_type(first_type)   && is_literal_integer_type(second_type))
    {return ((sizeoftype(first_type)  >= sizeoftype(second_type))? first_type :NULL);}
  if (is_ANY_INT_type(second_type)  && is_literal_integer_type(first_type))
    {return ((sizeoftype(second_type) >= sizeoftype(first_type)) ? second_type:NULL);}

  if (is_ANY_REAL_type(first_type)  && is_literal_real_type(second_type))
    {return ((sizeoftype(first_type)  >= sizeoftype(second_type))? first_type :NULL);}
  if (is_ANY_REAL_type(second_type) && is_literal_real_type(first_type))
    {return ((sizeoftype(second_type) >= sizeoftype(first_type)) ? second_type:NULL);}

  /* no common type */
  return NULL;
}

/* Determine the common data type between two data types.
 * Unlike the common_type__() function, we stop the compiler with an ERROR
 *  if no common data type is found.
 */
symbol_c *visit_expression_type_c::common_type(symbol_c *first_type, symbol_c *second_type) {
  symbol_c *res = common_type__(first_type, second_type);
  if (NULL == res) ERROR;
  return res;
}


/* Return TRUE if there is a common data type, otherwise return FALSE
 */
bool visit_expression_type_c::is_compatible_type(symbol_c *first_type, symbol_c *second_type) {
  if (first_type == NULL || second_type == NULL) {ERROR;}
  return (NULL != common_type__(first_type, second_type));
}



#define is_num_type      is_ANY_NUM_type
#define is_integer_type  is_ANY_INT_type
#define is_real_type     is_ANY_REAL_type
#define is_binary_type   is_ANY_BIT_type
 /* actually the ROR, ROL, SHL, and SHR function also accept boolean type! */
#define is_nbinary_type  is_ANY_BIT_type  
#define compute_standard_function_default visit_expression_type_c::compute_standard_function_default
#define compute_standard_function_il visit_expression_type_c::compute_standard_function_il
#define search_expression_type_c visit_expression_type_c
#define search(x) search_f(x)
#define next() next_nf()
//     #define search_constant_type_c::constant_int_type_name  search_expression_type_c::integer
#define constant_int_type_name  integer
#define is_same_type is_compatible_type
#include "../absyntax_utils/search_type_code.c"
#undef is_same_type
#undef constant_int_type_name
//     #undef search_constant_type_c::constant_int_type_name
#undef next
#undef search
#undef compute_standard_function_default
#undef compute_standard_function_il
#undef search_expression_type_c
#undef is_real_type
#undef is_binary_type
#undef is_nbinary_type
#undef is_integer_type
#undef is_num_type






/* A helper function... */
symbol_c *visit_expression_type_c::compute_boolean_expression(symbol_c *left_type, symbol_c *right_type,
                                                              is_data_type_t is_data_type) {
  bool error = false;

  if (!(this->*is_data_type)(left_type)) {
    STAGE3_ERROR(left_type, left_type, "invalid data type of first operand.");
    error = true;
  }
  if (!(this->*is_data_type)(right_type)) {
    STAGE3_ERROR(right_type, right_type, "invalid data type of second operand.");
    error = true;
  }
  if (!is_compatible_type(left_type, right_type)) {
    STAGE3_ERROR(left_type, right_type, "type mismatch between operands.");
    error = true;
  }

  if (error)
    return NULL;
  else
    return common_type(left_type, right_type);
}


/* A helper function... */
symbol_c *visit_expression_type_c::compute_numeric_expression(symbol_c *left_type, symbol_c *right_type,
                                                              is_data_type_t is_data_type) {
  if (!(this->*is_data_type)(left_type))
    STAGE3_ERROR(left_type, right_type, "Both parts of the equation must be the same type.");
  if (!(this->*is_data_type)(right_type))
    STAGE3_ERROR(left_type, right_type, "Both parts of the equation must be the same type.");
  if (!is_compatible_type(left_type, right_type))
    STAGE3_ERROR(left_type, right_type, "Both parts of the equation must be the same type.");

  if (is_literal_integer_type(left_type) || is_literal_real_type(left_type)) {
    return right_type;
  } else {
    return left_type;
  }

  /* humour the compiler... */
  return NULL;
}






/* A helper function... */
/* check the semantics of a FB or Function non-formal call */
/* e.g. foo(1, 2, 3, 4);  */
void visit_expression_type_c::check_nonformal_call(symbol_c *f_call, symbol_c *f_decl, bool use_il_defvar) {
  symbol_c *call_param_value, *call_param_type, *param_type;
  identifier_c *param_name;
  function_param_iterator_c       fp_iterator(f_decl);
  function_call_param_iterator_c fcp_iterator(f_call);

  /* if use_il_defvar, then the first parameter for the call comes from the il_default_variable */
  if (use_il_defvar) {
    /* The first parameter of the function corresponds to the il_default_variable_type of the function call */
    do {
      param_name = fp_iterator.next();
      if(param_name == NULL) break;
      /*  The EN and ENO parameters are default parameters.
       *  In the non-formal invocation of a function there can be no assignment of
       * values to these parameters. Therefore, we ignore the parameters declared
       * in the function.
       */
    } while ((strcmp(param_name->value, "EN") == 0) || (strcmp(param_name->value, "ENO") == 0));
    /* If the function does not have any parameters (param_name == NULL)
     * then we cannot compare its type with the il_default_variable_type.
     */
    if(param_name != NULL) {
      param_type = fp_iterator.param_type();
      if(!is_compatible_type(il_default_variable_type,param_type)) 
        STAGE3_ERROR(f_call, f_call, "In function/FB call, first parameter has invalid data type.");
    }
  } // if (use_il_defvar)

  /* Iterating through the non-formal parameters of the function call */
  while((call_param_value = fcp_iterator.next_nf()) != NULL) {
    /* Obtaining the type of the current parameter in the function call */
    call_param_type = base_type((symbol_c*)call_param_value->accept(*this));
    if (call_param_type == NULL) STAGE3_ERROR(call_param_value, call_param_value, "Could not determine data type of value being passed in function/FB call.");;

    /* 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 parameter declared with that name */
      if(param_name == NULL) {STAGE3_ERROR(f_call, f_call, "Too many parameters in function/FB call."); break;}
    } while ((strcmp(param_name->value, "EN") == 0) || (strcmp(param_name->value, "ENO") == 0));

    if(param_name != NULL) {
      /* Get the parameter type */
      param_type = fp_iterator.param_type();
      /* If the declared parameter and the parameter from the function call do no have the same type */
      if(!is_compatible_type(call_param_type,param_type)) STAGE3_ERROR(call_param_value, call_param_value, "Type mismatch in function/FB call parameter.");
    }
  }
}

void visit_expression_type_c::compute_input_operatores(symbol_c *symbol, const char *input_operator){
  symbol_c *call_param_type;
  symbol_c *fb_decl = il_operand_type;
    /* The following should never occur. The function block must be defined, 
     * and the FB type being called MUST be in the symtable... 
     * This was all already checked at stage 2!
     */
  if (NULL == fb_decl){ 
    STAGE3_ERROR(symbol, symbol, "Parameter operator needs an instance of a function block operand.");
    ERROR;
  }

   /* Iterating through the formal parameters of the function call */
  identifier_c call_param_name(input_operator);

  /* Obtaining the type of the value being passed in the function call */
  call_param_type = il_default_variable_type;
  if (call_param_type == NULL) {
    STAGE3_ERROR(&call_param_name, &call_param_name, "Could not determine data type of value being passed in function/FB call.");
    /* The data value being passed is possibly any enumerated type value.
     * We do not yet handle semantic verification of enumerated types.
     */
    ERROR;
  }
  call_param_type = base_type(call_param_type);
  if (call_param_type == NULL) STAGE3_ERROR(&call_param_name, &call_param_name, "Could not determine data type of value being passed in function/FB call.");
  

  check_formal_parameter(&call_param_name, call_param_type, fb_decl);
//   return NULL;
}

void visit_expression_type_c::check_formal_parameter(symbol_c *call_param_name, symbol_c *call_param_type, symbol_c *f_decl) {
  symbol_c *param_type;
  identifier_c *param_name;
  function_param_iterator_c       fp_iterator(f_decl);

  /* Find the corresponding parameter of the function being called */
  param_name = fp_iterator.search(call_param_name);
  if(param_name == NULL) {
    STAGE3_ERROR(call_param_name, call_param_name, "Invalid parameter in function/FB call.");
  } else {
    /* Get the parameter type */
    param_type = fp_iterator.param_type();
    /* If the declared parameter and the parameter from the function call have the same type */
//     if(!is_compatible_type(call_param_type, param_type)) STAGE3_ERROR(call_param_name, call_param_value, "Type mismatch function/FB call parameter.");
    if(!is_compatible_type(call_param_type, param_type)) STAGE3_ERROR(call_param_name, call_param_name, "Type mismatch function/FB call parameter.");
  }
}


/* A helper function... */
/* check the semantics of a FB or Function formal call */
/* e.g. foo(IN1 := 1, OUT1 =>x, EN := true);  */
void visit_expression_type_c::check_formal_call(symbol_c *f_call, symbol_c *f_decl) {
  symbol_c *call_param_value, *call_param_type, *call_param_name, *param_type;
  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);

  /* 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;

    /* Checking if there are duplicated parameter values */
    verify_duplicate_param = fcp_iterator.search_f(call_param_name);
    if(verify_duplicate_param != call_param_value){
      STAGE3_ERROR(call_param_name, verify_duplicate_param, "Duplicated parameter values.");
    }   

    /* Obtaining the type of the value being passed in the function call */
    call_param_type = (symbol_c*)call_param_value->accept(*this);
    if (call_param_type == NULL) {
      STAGE3_ERROR(call_param_name, call_param_value, "Could not determine data type of value being passed in function/FB call.");
      /* The data value being passed is possibly any enumerated type value.
       * We do not yet handle semantic verification of enumerated types.
       */
      ERROR;
    }
    call_param_type = base_type(call_param_type);
    if (call_param_type == NULL) STAGE3_ERROR(call_param_name, call_param_value, "Could not determine data type of value being passed in function/FB call.");

    /* Find the corresponding parameter of the function being called */
    param_name = fp_iterator.search(call_param_name);
    if(param_name == NULL) {
      STAGE3_ERROR(call_param_name, call_param_name, "Invalid parameter in function/FB call.");
    } else {
      /* Get the parameter type */
      param_type = fp_iterator.param_type();
      /* If the declared parameter and the parameter from the function call have the same type */
      if(!is_compatible_type(call_param_type, param_type)) STAGE3_ERROR(call_param_name, call_param_value, "Type mismatch function/FB call parameter.");
    }
  }
}




/* a helper function... */
symbol_c *visit_expression_type_c::base_type(symbol_c *symbol) {
  return (symbol_c *)symbol->accept(search_base_type);
}


/* a helper function... */
void *visit_expression_type_c::verify_null(symbol_c *symbol){
  if(il_default_variable_type == NULL){
    STAGE3_ERROR(symbol, symbol, "Il default variable can't be NULL.");
  }
  if(il_operand_type == NULL){
    STAGE3_ERROR(symbol, symbol, "function requires an operand.");
  }
  return NULL;
}




/*********************/
/* B 1.4 - Variables */
/*********************/

void *visit_expression_type_c::visit(symbolic_variable_c *symbol) {
  return search_varfb_instance_type->get_type(symbol);
}

/********************************************/
/* B 1.4.1 - Directly Represented Variables */
/********************************************/
void *visit_expression_type_c::visit(direct_variable_c *symbol) {
  switch (symbol->value[2]) {
    case 'X': // bit - 1 bit
      return (void *)&bool_type_name;
    case 'B': // byte - 8 bits
      return (void *)&byte_type_name;
    case 'W': // word - 16 bits
      return (void *)&word_type_name;
    case 'D': // double word - 32 bits
      return (void *)&dword_type_name;
    case 'L': // long word - 64 bits
      return (void *)&lword_type_name;
    default:  // if none of the above, then the empty string was used <=> boolean 
      return (void *)&bool_type_name;
   }
}

/*************************************/
/* B 1.4.2 - Multi-element variables */
/*************************************/
void *visit_expression_type_c::visit(array_variable_c *symbol) {
  return search_varfb_instance_type->get_type(symbol);
}

void *visit_expression_type_c::visit(structured_variable_c *symbol) {
  return search_varfb_instance_type->get_type(symbol);
}



/****************************************/
/* B.2 - Language IL (Instruction List) */
/****************************************/
/***********************************/
/* B 2.1 Instructions and Operands */
/***********************************/
/*| instruction_list il_instruction */
/* 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 *visit_expression_type_c::visit(instruction_list_c *symbol)

/* | label ':' [il_incomplete_instruction] eol_list */
//SYM_REF2(il_instruction_c, label, il_instruction)
// void *visit_expression_type_c::visit(il_instruction_c *symbol);


/* | il_simple_operator [il_operand] */
// SYM_REF2(il_simple_operation_c, il_simple_operator, il_operand)
void *visit_expression_type_c::visit(il_simple_operation_c *symbol) {
  if (il_error)
    return NULL;

  /* determine the data type of the operand */
  if (symbol->il_operand != NULL){
    il_operand_type = base_type((symbol_c *)symbol->il_operand->accept(*this));
  } else {
    il_operand_type = NULL;
  }
  /* recursive call to see whether data types are compatible */
  symbol->il_simple_operator->accept(*this);

  il_operand_type = NULL;
  return NULL;
}

// | function_name [il_operand_list] */
//SYM_REF2(il_function_call_c, function_name, il_operand_list)
void *visit_expression_type_c::visit(il_function_call_c *symbol) {
  if (il_error)
    return NULL;

  /* First find the declaration of the function being called! */
  function_declaration_c *f_decl = function_symtable.find_value(symbol->function_name);

  symbol_c *return_data_type = NULL;

  if (f_decl == function_symtable.end_value()) {
    function_type_t current_function_type = get_function_type((identifier_c *)symbol->function_name);
    if (current_function_type == function_none) ERROR;
    /*  This code is for the functions that the user did not declare and that are
     * part of the IL or ST languagem (built-in functions).
     *  For now we won't do the semantics analysis for that kind of functions.
    */
    /*  
    return_data_type = (symbol_c *)search_expression_type->compute_standard_function_default(NULL, symbol);
    if (NULL == return_data_type) ERROR;

    function_call_param_iterator_c fcp_iterator(symbol);

    int nb_param = 0;
    if (symbol->il_param_list != NULL)
      nb_param += ((list_c *)symbol->il_param_list)->n;

    identifier_c en_param_name("EN");*/
    /* Get the value from EN param */
    /*symbol_c *EN_param_value = fcp_iterator.search(&en_param_name);
    if (EN_param_value == NULL)
      EN_param_value = (symbol_c*)(new boolean_literal_c((symbol_c*)(new bool_type_name_c()), new boolean_true_c()));
    else
      nb_param --;
    ADD_PARAM_LIST(EN_param_value, (symbol_c*)(new bool_type_name_c()), function_param_iterator_c::direction_in)

    identifier_c eno_param_name("EN0");*/
    /* Get the value from ENO param */
    /*symbol_c *ENO_param_value = fcp_iterator.search(&eno_param_name);
    if (ENO_param_value != NULL)
      nb_param --;
    ADD_PARAM_LIST(ENO_param_value, (symbol_c*)(new bool_type_name_c()), function_param_iterator_c::direction_out)
    
    #include "st_code_gen.c"
    */
  } else {
    /* determine the base data type returned by the function being called... */
    return_data_type = base_type(f_decl->type_name);
    /* If the following occurs, then we must have some big bug in the syntax parser (stage 2)... */
    if (NULL == return_data_type) ERROR;

    /* check semantics of data passed in the function call... */
    check_nonformal_call(symbol, f_decl, true);

    /* set the new ddata type of the default variable for the following verifications... */
    il_default_variable_type = return_data_type;
  }
  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 *visit_expression_type_c::visit(il_expression_c *symbol) {
  if (il_error)
    return NULL;

  symbol_c *il_default_variable_type_back = il_default_variable_type;

  il_parenthesis_level++;

  if(symbol->il_operand != NULL) {
     il_default_variable_type = base_type((symbol_c *)symbol->il_operand->accept(*this));
  } else {
     il_default_variable_type = NULL;
  }

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

  il_parenthesis_level--;
  if (il_parenthesis_level < 0) ERROR;

  il_operand_type = il_default_variable_type;
  il_default_variable_type = il_default_variable_type_back;

  /* Now check the if the data type semantics of operation are correct,
   * but only if no previous error has been found...
   */
  if (il_error)
    return NULL;
  symbol->il_expr_operator->accept(*this);

  return NULL;
}


#if 0
/*  il_jump_operator label */
SYM_REF2(il_jump_operation_c, il_jump_operator, label)
void *visit_expression_type_c::visit(il_jump_operation_c *symbol);
#endif


/*   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 ')'
 */
/* SYM_REF4(il_fb_call_c, il_call_operator, fb_name, il_operand_list, il_param_list) */
void *visit_expression_type_c::visit(il_fb_call_c *symbol) {
  if (il_error)
    return NULL;

  /* first check whether the il_default_variable is of the correct type
   * for the CAL / CALC / CALCN operator being used...
   */
  symbol->il_call_operator->accept(*this);

  /* Now check the FB call itself... */

  /* First we find the declaration of the FB type of the FB instance being called... */
  /* e.g.  Function_block foo_fb_type
   *         ...
   *       End_Function_Block
   *
   *       Program test
   *         var fb1 : foo_fb_type; end_var
   *         fb1(...)
   *       End_Program
   *
   *    search_varfb_instance_type->get_type( identifier_c("fb1") )
   *    in the scope of Program 'test'
   *    will return the fb declaration of foo_fb_type !!
   */
#if 0
  symbol_c *fb_decl_symbol = search_varfb_instance_type->get_type(symbol->fb_name);
    /* The following should never occur. The function block must be defined, 
     * and the FB type being called MUST be in the symtable... 
     * This was all already checked at stage 2!
     */
  if (NULL == fb_decl_symbol) ERROR;

  function_block_declaration_c *fb_decl = dynamic_cast<function_block_declaration_c *>(fb_decl_symbol);
    /* should never occur. ... */
  if (NULL == fb_decl) ERROR;
#endif
  symbol_c *fb_decl = search_varfb_instance_type->get_type(symbol->fb_name);
    /* The following should never occur. The function block must be defined, 
     * and the FB type being called MUST be in the symtable... 
     * This was all already checked at stage 2!
     */
  if (NULL == fb_decl) ERROR;

  /* now check the semantics of the fb call... */
  /* If the syntax parser is working correctly, exactly one of the 
   * following two symbols will be NULL, while the other is != NULL.
   */
  if (NULL != symbol->il_operand_list)  check_nonformal_call(symbol, fb_decl);
  if (NULL != symbol->il_param_list)    check_formal_call   (symbol, fb_decl);

  return NULL;
}



/* | function_name '(' eol_list [il_param_list] ')' */
/* SYM_REF2(il_formal_funct_call_c, function_name, il_param_list) */
void *visit_expression_type_c::visit(il_formal_funct_call_c *symbol) {
  if (il_error)
    return NULL;

  function_declaration_c *f_decl = function_symtable.find_value(symbol->function_name);

  symbol_c *return_data_type = NULL;

  if (f_decl == function_symtable.end_value()) {
    function_type_t current_function_type = get_function_type((identifier_c *)symbol->function_name);
    if (current_function_type == function_none) ERROR;
    
    /*  This code is for the functions that the user did not declare and that are
     * part of the IL or ST languagem (built-in functions).
     *  For now we won't do the semantics analysis for that kind of functions.
    */
    #if 0
    return_data_type = (symbol_c *)search_expression_type->compute_standard_function_default(NULL, symbol);
    if (NULL == return_data_type) ERROR;
    
    function_call_param_iterator_c fcp_iterator(symbol);
    
    int nb_param = 0;
    if (symbol->il_param_list != NULL)
      nb_param += ((list_c *)symbol->il_param_list)->n;
    
    identifier_c en_param_name("EN");
    /* Get the value from EN param */
    symbol_c *EN_param_value = fcp_iterator.search(&en_param_name);
    if (EN_param_value == NULL)
      EN_param_value = (symbol_c*)(new boolean_literal_c((symbol_c*)(new bool_type_name_c()), new boolean_true_c()));
    else
      nb_param --;
    ADD_PARAM_LIST(EN_param_value, (symbol_c*)(new bool_type_name_c()), function_param_iterator_c::direction_in)
    
    identifier_c eno_param_name("EN0");
    /* Get the value from ENO param */
    symbol_c *ENO_param_value = fcp_iterator.search(&eno_param_name);
    if (ENO_param_value != NULL)
      nb_param --;
    ADD_PARAM_LIST(ENO_param_value, (symbol_c*)(new bool_type_name_c()), function_param_iterator_c::direction_out)
    
    #include "st_code_gen.c"
    #endif
  } else {
    /* determine the base data type returned by the function being called... */
    return_data_type = base_type(f_decl->type_name);
    /* the following should never occur. If it does, then we have a bug in the syntax parser (stage 2)... */
    if (NULL == return_data_type) ERROR;

    /* check semantics of data passed in the function call... */
    check_formal_call(symbol, f_decl);

    /* the data type of the data returned by the function, and stored in the il default variable... */
    il_default_variable_type = return_data_type;
  }
  return NULL;
}


#if 0
/* | il_operand_list ',' il_operand */
SYM_LIST(il_operand_list_c)
void *visit_expression_type_c::visit(il_operand_list_c *symbol);

/* | simple_instr_list il_simple_instruction */
SYM_LIST(simple_instr_list_c)
void *visit_expression_type_c::visit(simple_instr_list_c *symbol);

/* | il_initial_param_list il_param_instruction */
SYM_LIST(il_param_list_c)
void *visit_expression_type_c::visit(il_param_list_c *symbol);

/*  il_assign_operator il_operand
 * | il_assign_operator '(' eol_list simple_instr_list ')'
 */
SYM_REF3(il_param_assignment_c, il_assign_operator, il_operand, simple_instr_list)
void *visit_expression_type_c::visit(il_param_assignment_c *symbol);
/*  il_assign_out_operator variable */
SYM_REF2(il_param_out_assignment_c, il_assign_out_operator, variable)
void *visit_expression_type_c::visit(il_param_out_assignment_c *symbol);

#endif


/*******************/
/* B 2.2 Operators */
/*******************/

//SYM_REF0(LD_operator_c)
void *visit_expression_type_c::visit(LD_operator_c *symbol) {
  if (0 == il_parenthesis_level)
    il_error = false;

  if(il_operand_type == NULL)
      STAGE3_ERROR(symbol, symbol, "LD operator requires an operand.");
  il_default_variable_type = il_operand_type;
  return NULL;
}

// SYM_REF0(LDN_operator_c)
void *visit_expression_type_c::visit(LDN_operator_c *symbol) {
  if(il_operand_type == NULL)
      STAGE3_ERROR(symbol, symbol, "LDN operator requires an operand.");
  if(!is_ANY_BIT_type(il_operand_type))
      STAGE3_ERROR(symbol, symbol, "invalid data type of LDN operand, should be of type ANY_BIT.");
  il_default_variable_type = il_operand_type;
  return NULL;
}

// SYM_REF0(ST_operator_c)
void *visit_expression_type_c::visit(ST_operator_c *symbol) {
  verify_null(symbol);
  if(!is_compatible_type(il_default_variable_type, il_operand_type))
    STAGE3_ERROR(symbol, symbol, "Type mismatch in ST operation.");
  /* TODO: check whether il_operand_type is an LVALUE !! */
  /* data type of il_default_variable_type is unchanged... */
  // il_default_variable_type = il_default_variable_type;
  return NULL;
}

// SYM_REF0(STN_operator_c)
 void *visit_expression_type_c::visit(STN_operator_c *symbol) {
  verify_null(symbol);
  if(!is_compatible_type(il_default_variable_type, il_operand_type))
    STAGE3_ERROR(symbol, symbol, "Type mismatch in ST operation.");
  /* TODO: check whether il_operand_type is an LVALUE !! */
  if(!is_ANY_BIT_type(il_default_variable_type))
      STAGE3_ERROR(symbol, symbol, "invalid data type of il_default_variable for STN operand, should be of type ANY_BIT.");
  if(!is_ANY_BIT_type(il_operand_type))
      STAGE3_ERROR(symbol, symbol, "invalid data type of STN operand, should be of type ANY_BIT.");
  /* data type of il_default_variable_type is unchanged... */
  // il_default_variable_type = il_default_variable_type;
  return NULL;
}

//SYM_REF0(NOT_operator_c)
void *visit_expression_type_c::visit(NOT_operator_c *symbol) {
  if(il_operand_type != NULL){
    STAGE3_ERROR(symbol, symbol, "NOT operator may not have an operand.");
    return NULL;
  }
  if(il_default_variable_type == NULL) {
    STAGE3_ERROR(symbol, symbol, "Il default variable should not be NULL.");
    return NULL;
  }
  if(!is_ANY_BIT_type(il_default_variable_type)) {
    STAGE3_ERROR(symbol, symbol, "Il default variable should be of type ANY_BIT.");
    return NULL;
  }
  /* data type of il_default_variable_type is unchanged... */
  // il_default_variable_type = il_default_variable_type;
  return NULL;
}

// SYM_REF0(S_operator_c)
void *visit_expression_type_c::visit(S_operator_c *symbol) {
  verify_null(symbol);
  if (!is_BOOL_type(il_default_variable_type)) {STAGE3_ERROR(symbol, symbol, "IL default variable should be BOOL type.");}
  if (!is_BOOL_type(il_operand_type)) {STAGE3_ERROR(symbol, symbol, "operator S requires operand of type BOOL.");}
  /* TODO: check whether il_operand_type is an LVALUE !! */
  /* data type of il_default_variable_type is unchanged... */
  // il_default_variable_type = il_default_variable_type;
  return NULL;
}

// SYM_REF0(R_operator_c)
void *visit_expression_type_c::visit(R_operator_c *symbol) {
  verify_null(symbol);
  if (!is_BOOL_type(il_default_variable_type)) {STAGE3_ERROR(symbol, symbol, "IL default variable should be BOOL type.");}
  if (!is_BOOL_type(il_operand_type)) {STAGE3_ERROR(symbol, symbol, "operator R requires operand of type BOOL.");}
  /* TODO: check whether il_operand_type is an LVALUE !! */
  /* data type of il_default_variable_type is unchanged... */
  // il_default_variable_type = il_default_variable_type;
  return NULL;
}


// SYM_REF0(S1_operator_c)
void *visit_expression_type_c::visit(S1_operator_c *symbol){
  compute_input_operatores(symbol, "S1");
  return NULL;
}

// SYM_REF0(R1_operator_c)
void *visit_expression_type_c::visit(R1_operator_c *symbol) {
  compute_input_operatores(symbol, "R1");
  return NULL;
}

// SYM_REF0(CLK_operator_c)
void *visit_expression_type_c::visit(CLK_operator_c *symbol) {
  compute_input_operatores(symbol, "CLK");
  return NULL;
}

// SYM_REF0(CU_operator_c)
void *visit_expression_type_c::visit(CU_operator_c *symbol) {
  compute_input_operatores(symbol, "CU");
  return NULL;
}

// SYM_REF0(CD_operator_c)
void *visit_expression_type_c::visit(CD_operator_c *symbol) {
  compute_input_operatores(symbol, "CD");
  return NULL;
}

// SYM_REF0(PV_operator_c)
void *visit_expression_type_c::visit(PV_operator_c *symbol) {
  compute_input_operatores(symbol, "PV");
  return NULL;
}

// SYM_REF0(IN_operator_c)
void *visit_expression_type_c::visit(IN_operator_c *symbol) {
  compute_input_operatores(symbol, "IN");
  return NULL;
}

// SYM_REF0(PT_operator_c)
void *visit_expression_type_c::visit(PT_operator_c *symbol) {
  compute_input_operatores(symbol, "PT");
  return NULL;
}

//SYM_REF0(AND_operator_c)
void *visit_expression_type_c::visit(AND_operator_c *symbol) {
  verify_null(symbol);
  il_default_variable_type = compute_boolean_expression(il_default_variable_type,  il_operand_type, &visit_expression_type_c::is_ANY_BIT_type);
  return NULL;
}

//SYM_REF0(OR_operator_c)
void *visit_expression_type_c::visit(OR_operator_c *symbol) {
  verify_null(symbol);
  il_default_variable_type = compute_boolean_expression(il_default_variable_type,  il_operand_type, &visit_expression_type_c::is_ANY_BIT_type);
  return NULL;
}

//SYM_REF0(XOR_operator_c)
void *visit_expression_type_c::visit(XOR_operator_c *symbol) {
  verify_null(symbol);
  il_default_variable_type = compute_boolean_expression(il_default_variable_type,  il_operand_type, &visit_expression_type_c::is_ANY_BIT_type);
  return NULL;
}

// SYM_REF0(ANDN_operator_c)
void *visit_expression_type_c::visit(ANDN_operator_c *symbol) {
  verify_null(symbol);
  il_default_variable_type = compute_boolean_expression(il_default_variable_type,  il_operand_type, &visit_expression_type_c::is_ANY_BIT_type);
  return NULL;
}

// SYM_REF0(ORN_operator_c)
void *visit_expression_type_c::visit(ORN_operator_c *symbol) {
  verify_null(symbol);
  il_default_variable_type = compute_boolean_expression(il_default_variable_type,  il_operand_type, &visit_expression_type_c::is_ANY_BIT_type);
  return NULL;
}

// SYM_REF0(XORN_operator_c)
void *visit_expression_type_c::visit(XORN_operator_c *symbol) {
  verify_null(symbol);
  il_default_variable_type = compute_boolean_expression(il_default_variable_type,  il_operand_type, &visit_expression_type_c::is_ANY_BIT_type);
  return NULL;
}

// SYM_REF0(ADD_operator_c)
void *visit_expression_type_c::visit(ADD_operator_c *symbol) {
  verify_null(symbol);
  symbol_c *left_type  = il_default_variable_type;
  symbol_c *right_type = il_operand_type;
  if      (typeid(*left_type) == typeid(time_type_name_c) && typeid(*right_type) == typeid(time_type_name_c)) 
    il_default_variable_type = &time_type_name;
  else if (typeid(*left_type) == typeid(tod_type_name_c)  && typeid(*right_type) == typeid(time_type_name_c)) 
    il_default_variable_type = &tod_type_name;
  else if (typeid(*left_type) == typeid(dt_type_name_c)   && typeid(*right_type) == typeid(time_type_name_c)) 
    il_default_variable_type = &dt_type_name;
  else il_default_variable_type = compute_numeric_expression(il_default_variable_type, il_operand_type, &visit_expression_type_c::is_ANY_MAGNITUDE_type);
  return NULL;
}

// SYM_REF0(SUB_operator_c)
void *visit_expression_type_c::visit(SUB_operator_c *symbol) {
  verify_null(symbol);
  symbol_c *left_type = il_default_variable_type;
  symbol_c *right_type = il_operand_type;;
  if      (typeid(*left_type) == typeid(time_type_name_c) && typeid(*right_type) == typeid(time_type_name_c))
    il_default_variable_type = &time_type_name;
  else if (typeid(*left_type) == typeid(date_type_name_c) && typeid(*right_type) == typeid(date_type_name_c))
    il_default_variable_type = &time_type_name;
  else if (typeid(*left_type) == typeid(tod_type_name_c)  && typeid(*right_type) == typeid(time_type_name_c))
    il_default_variable_type = &tod_type_name;
  else if (typeid(*left_type) == typeid(tod_type_name_c)  && typeid(*right_type) == typeid(tod_type_name_c))
    il_default_variable_type = &time_type_name;
  else if (typeid(*left_type) == typeid(dt_type_name_c)   && typeid(*right_type) == typeid(time_type_name_c))
    il_default_variable_type = &dt_type_name;
  else if (typeid(*left_type) == typeid(dt_type_name_c)   && typeid(*right_type) == typeid(dt_type_name_c))
    il_default_variable_type = &time_type_name;
  else il_default_variable_type = compute_numeric_expression(il_default_variable_type, il_operand_type, &visit_expression_type_c::is_ANY_MAGNITUDE_type);
  return NULL;
}

// SYM_REF0(MUL_operator_c)
void *visit_expression_type_c::visit(MUL_operator_c *symbol) {
  verify_null(symbol);
  symbol_c *left_type = il_default_variable_type;
  symbol_c *right_type = il_operand_type;
  if (typeid(*left_type) == typeid(time_type_name_c) && is_ANY_NUM_type(right_type))
    il_default_variable_type = &time_type_name;
  else il_default_variable_type = compute_numeric_expression(il_default_variable_type, il_operand_type, &visit_expression_type_c::is_ANY_NUM_type);
  return NULL;
}

// SYM_REF0(DIV_operator_c)
void *visit_expression_type_c::visit(DIV_operator_c *symbol) {
  verify_null(symbol);
  symbol_c *left_type = il_default_variable_type;
  symbol_c *right_type = il_operand_type;
  if (typeid(*left_type) == typeid(time_type_name_c) && is_ANY_NUM_type(right_type))
    il_default_variable_type = &time_type_name;
  else il_default_variable_type = compute_numeric_expression(il_default_variable_type, il_operand_type, &visit_expression_type_c::is_ANY_NUM_type);
  return NULL;
}

// SYM_REF0(MOD_operator_c)
void *visit_expression_type_c::visit(MOD_operator_c *symbol) {
  verify_null(symbol);
  il_default_variable_type = compute_numeric_expression(il_default_variable_type, il_operand_type, &visit_expression_type_c::is_ANY_INT_type); 
  return NULL;
}

// SYM_REF0(GT_operator_c)
void *visit_expression_type_c::visit(GT_operator_c *symbol) {
  verify_null(symbol);
  compute_boolean_expression(il_default_variable_type, il_operand_type, &visit_expression_type_c::is_ANY_ELEMENTARY_type);
  il_default_variable_type = &search_expression_type_c::bool_type_name;
  return NULL;
}

//SYM_REF0(GE_operator_c)
void *visit_expression_type_c::visit(GE_operator_c *symbol) {
  verify_null(symbol);
  compute_boolean_expression(il_default_variable_type, il_operand_type, &visit_expression_type_c::is_ANY_ELEMENTARY_type);
  il_default_variable_type = &search_expression_type_c::bool_type_name;
  return NULL;
}

//SYM_REF0(EQ_operator_c)
void *visit_expression_type_c::visit(EQ_operator_c *symbol) {
  verify_null(symbol);
  compute_boolean_expression(il_default_variable_type, il_operand_type, &visit_expression_type_c::is_ANY_ELEMENTARY_type);
  il_default_variable_type = &search_expression_type_c::bool_type_name;
  return NULL;
}

//SYM_REF0(LT_operator_c)
void *visit_expression_type_c::visit(LT_operator_c *symbol) {
  verify_null(symbol);
  compute_boolean_expression(il_default_variable_type, il_operand_type, &visit_expression_type_c::is_ANY_ELEMENTARY_type);
  il_default_variable_type = &search_expression_type_c::bool_type_name;
  return NULL;
}

//SYM_REF0(LE_operator_c)
void *visit_expression_type_c::visit(LE_operator_c *symbol) {
  verify_null(symbol);
  compute_boolean_expression(il_default_variable_type, il_operand_type, &visit_expression_type_c::is_ANY_ELEMENTARY_type);
  il_default_variable_type = &search_expression_type_c::bool_type_name;
  return NULL;
}

//SYM_REF0(NE_operator_c)
void *visit_expression_type_c::visit(NE_operator_c *symbol) {
  verify_null(symbol);
  compute_boolean_expression(il_default_variable_type, il_operand_type, &visit_expression_type_c::is_ANY_ELEMENTARY_type);
  il_default_variable_type = &search_expression_type_c::bool_type_name;
  return NULL;
}

// SYM_REF0(CAL_operator_c)
void *visit_expression_type_c::visit(CAL_operator_c *symbol) {
  return NULL;
}

// SYM_REF0(CALC_operator_c)
void *visit_expression_type_c::visit(CALC_operator_c *symbol) {
  if(il_default_variable_type == NULL)
    STAGE3_ERROR(symbol, symbol, "CALC: il default variable should not be NULL.");
  if (!is_BOOL_type(il_default_variable_type))
    STAGE3_ERROR(symbol, symbol, "CALC operator requires il_default_variable to be of type BOOL.");
  return NULL;
}

// SYM_REF0(CALCN_operator_c)
void *visit_expression_type_c::visit(CALCN_operator_c *symbol) {
  if(il_default_variable_type == NULL)
    STAGE3_ERROR(symbol, symbol, "CALCN: il_default_variable should not be NULL.");
  if (!is_BOOL_type(il_default_variable_type))
    STAGE3_ERROR(symbol, symbol, "CALCN operator requires il_default_variable to be of type BOOL.");
  return NULL;
}

// SYM_REF0(RET_operator_c)
void *visit_expression_type_c::visit(RET_operator_c *symbol) {
  return NULL;
}

// SYM_REF0(RETC_operator_c)
void *visit_expression_type_c::visit(RETC_operator_c *symbol) {
  if(il_default_variable_type == NULL)
    STAGE3_ERROR(symbol, symbol, "RETC: il default variable should not be NULL.");
  if (!is_BOOL_type(il_default_variable_type))
    STAGE3_ERROR(symbol, symbol, "RETC operator requires il_default_variable to be of type BOOL.");
  return NULL;
}

// SYM_REF0(RETCN_operator_c)
void *visit_expression_type_c::visit(RETCN_operator_c *symbol) {
  if(il_default_variable_type == NULL)
    STAGE3_ERROR(symbol, symbol, "RETCN: il_default_variable should not be NULL.");
  if (!is_BOOL_type(il_default_variable_type))
    STAGE3_ERROR(symbol, symbol, "RETCN operator requires il_default_variable to be of type BOOL.");
  return NULL;
}

// SYM_REF0(JMP_operator_c)
void *visit_expression_type_c::visit(JMP_operator_c *symbol){
  return NULL;
}

// SYM_REF0(JMPC_operator_c)
void *visit_expression_type_c::visit(JMPC_operator_c *symbol) {
  if(il_default_variable_type == NULL)
    STAGE3_ERROR(symbol, symbol, "JMPC: il default variable should not be NULL.");
  if (!is_BOOL_type(il_default_variable_type))
    STAGE3_ERROR(symbol, symbol, "JMPC operator requires il_default_variable to be of type BOOL.");
  return NULL;
}

// SYM_REF0(JMPCN_operator_c)
void *visit_expression_type_c::visit(JMPCN_operator_c *symbol) {
  if(il_default_variable_type == NULL)
    STAGE3_ERROR(symbol, symbol, "JMPCN: il_default_variable should not be NULL.");
  if (!is_BOOL_type(il_default_variable_type))
    STAGE3_ERROR(symbol, symbol, "JMPCN operator requires il_default_variable to be of type BOOL.");
  return NULL;
}

/* Symbol class handled together with function call checks */
/*  any_identifier ASSIGN */
// SYM_REF1(il_assign_operator_c, variable_name)
// void *visit_expression_type_c::visit(il_assign_operator_c *symbol, variable_name);

/* Symbol class handled together with function call checks */
/*| [NOT] any_identifier SENDTO */
// SYM_REF2(il_assign_out_operator_c, option, variable_name)
// void *visit_expression_type_c::visit(il_assign_operator_c *symbol, option, variable_name);





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

void *visit_expression_type_c::visit(or_expression_c *symbol) {
  symbol_c *left_type = base_type((symbol_c *)symbol->l_exp->accept(*this));
  symbol_c *right_type = base_type((symbol_c *)symbol->r_exp->accept(*this));
  return compute_boolean_expression(left_type, right_type, &visit_expression_type_c::is_ANY_BIT_type);
}


void *visit_expression_type_c::visit(xor_expression_c *symbol) {
  symbol_c *left_type = base_type((symbol_c *)symbol->l_exp->accept(*this));
  symbol_c *right_type = base_type((symbol_c *)symbol->r_exp->accept(*this));
  return compute_boolean_expression(left_type, right_type, &visit_expression_type_c::is_ANY_BIT_type);
}


void *visit_expression_type_c::visit(and_expression_c *symbol) {
  symbol_c *left_type = base_type((symbol_c *)symbol->l_exp->accept(*this));
  symbol_c *right_type = base_type((symbol_c *)symbol->r_exp->accept(*this));
  return compute_boolean_expression(left_type, right_type, &visit_expression_type_c::is_ANY_BIT_type);
}


void *visit_expression_type_c::visit(equ_expression_c *symbol) {
  symbol_c *left_type = base_type((symbol_c *)symbol->l_exp->accept(*this));
  symbol_c *right_type = base_type((symbol_c *)symbol->r_exp->accept(*this));
  compute_boolean_expression(left_type, right_type, &visit_expression_type_c::is_ANY_ELEMENTARY_type);
  return &search_expression_type_c::bool_type_name;
}


void *visit_expression_type_c::visit(notequ_expression_c *symbol)  {
  symbol_c *left_type = base_type((symbol_c *)symbol->l_exp->accept(*this));
  symbol_c *right_type = base_type((symbol_c *)symbol->r_exp->accept(*this));
  compute_boolean_expression(left_type, right_type, &visit_expression_type_c::is_ANY_ELEMENTARY_type);
  return &search_expression_type_c::bool_type_name;
}


void *visit_expression_type_c::visit(lt_expression_c *symbol) {
  symbol_c *left_type  = base_type((symbol_c *)symbol->l_exp->accept(*this));
  symbol_c *right_type = base_type((symbol_c *)symbol->r_exp->accept(*this));
  compute_boolean_expression(left_type, right_type, &visit_expression_type_c::is_ANY_ELEMENTARY_type);
  return &search_expression_type_c::bool_type_name;
}


void *visit_expression_type_c::visit(gt_expression_c *symbol) {
  symbol_c *left_type  = base_type((symbol_c *)symbol->l_exp->accept(*this));
  symbol_c *right_type = base_type((symbol_c *)symbol->r_exp->accept(*this));
  compute_boolean_expression(left_type, right_type, &visit_expression_type_c::is_ANY_ELEMENTARY_type);
  return &search_expression_type_c::bool_type_name;
}


void *visit_expression_type_c::visit(le_expression_c *symbol) {
  symbol_c *left_type  = base_type((symbol_c *)symbol->l_exp->accept(*this));
  symbol_c *right_type = base_type((symbol_c *)symbol->r_exp->accept(*this));
  compute_boolean_expression(left_type, right_type, &visit_expression_type_c::is_ANY_ELEMENTARY_type);
  return &search_expression_type_c::bool_type_name;
}


void *visit_expression_type_c::visit(ge_expression_c *symbol) {
  symbol_c *left_type  = base_type((symbol_c *)symbol->l_exp->accept(*this));
  symbol_c *right_type = base_type((symbol_c *)symbol->r_exp->accept(*this));
  compute_boolean_expression(left_type, right_type, &visit_expression_type_c::is_ANY_ELEMENTARY_type);
  return &search_expression_type_c::bool_type_name;
}


void *visit_expression_type_c::visit(add_expression_c *symbol) {
  symbol_c *left_type  = base_type((symbol_c *)symbol->l_exp->accept(*this));
  symbol_c *right_type = base_type((symbol_c *)symbol->r_exp->accept(*this));
  if (typeid(*left_type) == typeid(time_type_name_c) && typeid(*right_type) == typeid(time_type_name_c)) {return (void *)&time_type_name;}
  if (typeid(*left_type) == typeid(tod_type_name_c) && typeid(*right_type) == typeid(time_type_name_c)) {return (void *)&tod_type_name;}
  if (typeid(*left_type) == typeid(dt_type_name_c) && typeid(*right_type) == typeid(time_type_name_c)) {return (void *)&dt_type_name;}
  return compute_numeric_expression(left_type, right_type, &visit_expression_type_c::is_ANY_MAGNITUDE_type);
}


void *visit_expression_type_c::visit(sub_expression_c *symbol) {
  symbol_c *left_type  = base_type((symbol_c *)symbol->l_exp->accept(*this));
  symbol_c *right_type = base_type((symbol_c *)symbol->r_exp->accept(*this));
  if (typeid(*left_type) == typeid(time_type_name_c) && typeid(*right_type) == typeid(time_type_name_c)) {return (void *)&time_type_name;}
  if (typeid(*left_type) == typeid(date_type_name_c) && typeid(*right_type) == typeid(date_type_name_c)) {return (void *)&time_type_name;}
  if (typeid(*left_type) == typeid(tod_type_name_c) && typeid(*right_type) == typeid(time_type_name_c)) {return (void *)&tod_type_name;}
  if (typeid(*left_type) == typeid(tod_type_name_c) && typeid(*right_type) == typeid(tod_type_name_c)) {return (void *)&time_type_name;}
  if (typeid(*left_type) == typeid(dt_type_name_c) && typeid(*right_type) == typeid(time_type_name_c)) {return (void *)&dt_type_name;}
  if (typeid(*left_type) == typeid(dt_type_name_c) && typeid(*right_type) == typeid(dt_type_name_c)) {return (void *)&time_type_name;}
  return compute_numeric_expression(left_type, right_type, &visit_expression_type_c::is_ANY_MAGNITUDE_type);
}


void *visit_expression_type_c::visit(mul_expression_c *symbol) {
  symbol_c *left_type  = base_type((symbol_c *)symbol->l_exp->accept(*this));
  symbol_c *right_type = base_type((symbol_c *)symbol->r_exp->accept(*this));
  if (typeid(*left_type) == typeid(time_type_name_c) && is_ANY_NUM_type(right_type)) {return (void *)&time_type_name;}
  return compute_numeric_expression(left_type, right_type, &visit_expression_type_c::is_ANY_NUM_type);
}


void *visit_expression_type_c::visit(div_expression_c *symbol) {
  symbol_c *left_type  = base_type((symbol_c *)symbol->l_exp->accept(*this));
  symbol_c *right_type = base_type((symbol_c *)symbol->r_exp->accept(*this));
  if (typeid(*left_type) == typeid(time_type_name_c) && is_ANY_NUM_type(right_type)){return (void *)&time_type_name;}
  return compute_numeric_expression(left_type, right_type, &visit_expression_type_c::is_ANY_NUM_type);
}


void *visit_expression_type_c::visit(mod_expression_c *symbol) {
  symbol_c *left_type  = base_type((symbol_c *)symbol->l_exp->accept(*this));
  symbol_c *right_type = base_type((symbol_c *)symbol->r_exp->accept(*this));
  return compute_numeric_expression(left_type, right_type, &visit_expression_type_c::is_ANY_INT_type);
}


void *visit_expression_type_c::visit(power_expression_c *symbol) {
  symbol_c *left_type  = base_type((symbol_c *)symbol->l_exp->accept(*this));
  symbol_c *right_type = base_type((symbol_c *)symbol->r_exp->accept(*this));
  if (!is_ANY_REAL_type(left_type))
    STAGE3_ERROR(symbol->l_exp, symbol->l_exp, "first operand of ** operator has invalid data type, should be of type ANY_REAL.");
  if (!is_ANY_NUM_type(right_type))
    STAGE3_ERROR(symbol->r_exp, symbol->r_exp, "second operand of ** operator has invalid data type, should be of type ANY_NUM.");

  return (void *)left_type;
}


void *visit_expression_type_c::visit(neg_expression_c *symbol) {
  symbol_c *exp_type = base_type((symbol_c *)symbol->exp->accept(*this));
  if (!is_ANY_MAGNITUDE_type(exp_type))
    STAGE3_ERROR(symbol, symbol, "operand of negate expression '-' has invalid data type, should be of type ANY_MAGNITUDE.");

  return exp_type;
}


void *visit_expression_type_c::visit(not_expression_c *symbol) {
  symbol_c *type = base_type((symbol_c *)symbol->exp->accept(*this));
  return compute_boolean_expression(type, type, &visit_expression_type_c::is_ANY_BIT_type);
}


void *visit_expression_type_c::visit(function_invocation_c *symbol) {
  function_declaration_c *f_decl = function_symtable.find_value(symbol->function_name);
  if (f_decl == function_symtable.end_value()) {
    /* TODO: the following code is for standard library functions. We do not yet support this... */
    void *res = compute_standard_function_default(symbol);
    if (res != NULL) return res;
    ERROR;
  }

  /* now check the semantics of the function call... */
  /* If the syntax parser is working correctly, exactly one of the 
   * following two symbols will be NULL, while the other is != NULL.
   */
  if (symbol->   formal_param_list != NULL) check_formal_call   (symbol, f_decl);
  if (symbol->nonformal_param_list != NULL) check_nonformal_call(symbol, f_decl);

  return base_type(f_decl->type_name);
}

/********************/
/* 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 *visit_expression_type_c::visit(statement_list_c *symbol)


/*********************************/
/* B 3.2.1 Assignment Statements */
/*********************************/

void *visit_expression_type_c::visit(assignment_statement_c *symbol) {
  symbol_c *left_type = base_type((symbol_c *)symbol->l_exp->accept(*this));
  symbol_c *right_type = base_type((symbol_c *)symbol->r_exp->accept(*this));

  if (!is_compatible_type(left_type, right_type))  {
     STAGE3_ERROR(symbol, symbol, "data type mismatch in assignment statement!\n");
  }
  return NULL;
}



/*****************************************/
/* B 3.2.2 Subprogram Control Statements */
/*****************************************/

/*  RETURN */
// SYM_REF0(return_statement_c)


/* fb_name '(' [param_assignment_list] ')' */
/* param_assignment_list -> may be NULL ! */
// SYM_REF3(fb_invocation_c, fb_name, formal_param_list, nonformal_param_list)
void *visit_expression_type_c::visit(fb_invocation_c *symbol) {
  symbol_c *fb_decl = search_varfb_instance_type->get_type(symbol->fb_name);
    /* The following should never occur. The function block must be defined, 
     * and the FB type being called MUST be in the symtable... 
     * This was all already checked at stage 2!
     */
  if (NULL == fb_decl) ERROR;

  /* now check the semantics of the fb call... */
  /* If the syntax parser is working correctly, exactly one of the 
   * following two symbols will be NULL, while the other is != NULL.
   */
  if (symbol->   formal_param_list != NULL) check_formal_call   (symbol, fb_decl);
  if (symbol->nonformal_param_list != NULL) check_nonformal_call(symbol, fb_decl);

  return NULL;
}


#if 0
/* helper symbol for fb_invocation */
/* param_assignment_list ',' param_assignment */
SYM_LIST(param_assignment_list_c)

/*  variable_name ASSIGN expression */
SYM_REF2(input_variable_param_assignment_c, variable_name, expression)

/* [NOT] variable_name '=>' variable */
SYM_REF3(output_variable_param_assignment_c, not_param, variable_name, variable)

/* helper CLASS for output_variable_param_assignment */
SYM_REF0(not_paramassign_c)
#endif

/********************************/
/* B 3.2.3 Selection Statements */
/********************************/

/* IF expression THEN statement_list elseif_statement_list ELSE statement_list END_IF */
// SYM_REF4(if_statement_c, expression, statement_list, elseif_statement_list, else_statement_list)
void *visit_expression_type_c::visit(if_statement_c *symbol) {
  symbol_c *expr_type = base_type((symbol_c*)symbol->expression->accept(*this));
  if (!is_BOOL_type(expr_type)) STAGE3_ERROR(symbol,symbol,"IF conditional expression is not of boolean type.");
  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;
}

/* helper symbol for if_statement */
// SYM_LIST(elseif_statement_list_c)
// void *visit_expression_type_c::visit(elseif_statement_list_c *symbol) { }

/* helper symbol for elseif_statement_list */
/* ELSIF expression THEN statement_list    */
// SYM_REF2(elseif_statement_c, expression, statement_list)
void *visit_expression_type_c::visit(elseif_statement_c *symbol) {
  symbol_c *elseif_expr_type = base_type((symbol_c*)symbol->expression->accept(*this));
  if(!is_BOOL_type(elseif_expr_type)) STAGE3_ERROR(symbol,symbol,"ELSIF conditional expression is not of boolean type.");
  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 *visit_expression_type_c::visit(case_statement_c *symbol) {
  case_expression_type = base_type((symbol_c*)symbol->expression->accept(*this));
  if (NULL != case_expression_type) {
    if (NULL != symbol->case_element_list)
      symbol->case_element_list->accept(*this);
  }
  if (NULL != symbol->statement_list)
    symbol->statement_list->accept(*this);
  return NULL;
}

#if 0
/* helper symbol for case_statement */
// SYM_LIST(case_element_list_c)
// void *visit_expression_type_c::visit(case_element_list_c *symbol);

/*  case_list ':' statement_list */
// SYM_REF2(case_element_c, case_list, statement_list)
void *visit_expression_type_c::visit(case_element_c *symbol);  
#endif

// SYM_LIST(case_list_c)
void *visit_expression_type_c::visit(case_list_c *symbol) {
  symbol_c *element_type;
  for(int i = 0; i < symbol->n; i++) {
    element_type = (symbol_c *)symbol->elements[i]->accept(*this);
    if (NULL == element_type) {
      STAGE3_ERROR(symbol->elements[i], symbol->elements[i], "Case list element has undefined data type.");
    } else {
      element_type = base_type(element_type);
      if (NULL != element_type){
        if (!is_compatible_type(case_expression_type, element_type))
          STAGE3_ERROR(symbol->elements[i], symbol->elements[i], "Invalid data type of case list element.");
      }
    }
  }
  return NULL;
}

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

/*  FOR control_variable ASSIGN expression TO expression [BY expression] DO statement_list END_FOR */
// SYM_REF5(for_statement_c, control_variable, beg_expression, end_expression, by_expression, statement_list)
void *visit_expression_type_c::visit(for_statement_c *symbol) {
  symbol_c *var_type = (symbol_c*)symbol->control_variable->accept(*this);
  if (NULL == var_type) ERROR;
  var_type = base_type(var_type);
  if (NULL == var_type) ERROR;
  // ASSIGN
  symbol_c *beg_expr_type = base_type((symbol_c*)symbol->beg_expression->accept(*this));
  if (NULL != beg_expr_type) { 
    if(!is_compatible_type(var_type,beg_expr_type)) 
      STAGE3_ERROR(symbol, symbol, "Data type mismatch between control variable and initial value.");
  }
  // TO
  symbol_c *end_expr_type = base_type((symbol_c*)symbol->end_expression->accept(*this));
  if (NULL != end_expr_type) { 
    if(!is_compatible_type(var_type,end_expr_type)) 
      STAGE3_ERROR(symbol, symbol, "Data type mismatch between control variable and final value.");
  }
  // BY
  if(symbol->by_expression != NULL) {
    symbol_c *by_expr_type = base_type((symbol_c*)symbol->by_expression->accept(*this));
    if (NULL != end_expr_type) {   
      if(!is_compatible_type(var_type,by_expr_type)) 
        STAGE3_ERROR(symbol, symbol, "Data type mismatch between control variable and BY value.");
    }
  }
  // DO
  if (NULL != symbol->statement_list)
    symbol->statement_list->accept(*this); 
  return NULL;
}


/*  WHILE expression DO statement_list END_WHILE */
// SYM_REF2(while_statement_c, expression, statement_list)
void *visit_expression_type_c::visit(while_statement_c *symbol) {
  symbol_c *expr_type = base_type((symbol_c*)symbol->expression->accept(*this));
  if (NULL != expr_type) {
    if(!is_BOOL_type(expr_type)) 
      STAGE3_ERROR(symbol,symbol,"WHILE conditional expression is not of boolean type.");
  }
 
  if (NULL != symbol->statement_list)
    symbol->statement_list->accept(*this); 
  return NULL;
}

/*  REPEAT statement_list UNTIL expression END_REPEAT */
// SYM_REF2(repeat_statement_c, statement_list, expression)
void *visit_expression_type_c::visit(repeat_statement_c *symbol) {
  if (NULL != symbol->statement_list)
    symbol->statement_list->accept(*this); 
 
  symbol_c *expr_type = base_type((symbol_c*)symbol->expression->accept(*this));
  if (NULL != expr_type) {
    if(!is_BOOL_type(expr_type)) 
      STAGE3_ERROR(symbol,symbol,"REPEAT conditional expression is not of boolean type.");
  }
  return NULL;
}

/*  EXIT */
// SYM_REF0(exit_statement_c)