diff -r 0c2ef191b22a -r d48f53715f77 stage3/fill_candidate_datatypes.cc
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/stage3/fill_candidate_datatypes.cc	Wed Feb 01 19:49:11 2012 +0000
@@ -0,0 +1,1830 @@
+/*
+ *  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;
+}
+
+void fill_candidate_datatypes_c::match_nonformal_call(symbol_c *f_call, symbol_c *f_decl, int *error_count) {
+	symbol_c *call_param_value,  *param_type;
+	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;
+
+	/* reset error counter */
+	if (error_count != NULL) *error_count = 0;
+	/* Iterating through the non-formal parameters of the function call */
+	while((call_param_value = fcp_iterator.next_nf()) != NULL) {
+		/* Obtaining the type of the value being passed in the function call */
+		std::vector <symbol_c *>&call_param_types = call_param_value->candidate_datatypes;
+		/* 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) {
+				(*error_count)++;
+				return;
+			}
+		} while ((strcmp(param_name->value, "EN") == 0) || (strcmp(param_name->value, "ENO") == 0));
+
+		/* Get the parameter type */
+		param_type = base_type(fp_iterator.param_type());
+		for(i = 0; i < call_param_types.size(); i++) {
+			/* If the declared parameter and the parameter from the function call do not have the same type */
+			if(is_type_equal(param_type, call_param_types[i])) {
+				break;
+			}
+		}
+		if (i >= call_param_types.size()) (*error_count)++;
+	}
+}
+
+void fill_candidate_datatypes_c::match_formal_call(symbol_c *f_call, symbol_c *f_decl, int *error_count) {
+	symbol_c *call_param_value, *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);
+	int extensible_parameter_highest_index = -1;
+	identifier_c *extensible_parameter_name;
+	unsigned int i;
+
+	/* reset error counter */
+	if (error_count != NULL) *error_count = 0;
+
+	/* 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)
+			(*error_count)++;
+
+		/* 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) {
+			(*error_count)++;
+		} else {
+			/* Get the parameter type */
+			param_type = base_type(fp_iterator.param_type());
+			for (i = 0; i < call_param_types.size(); i++) {
+				/* If the declared parameter and the parameter from the function call have the same type */
+				if(is_type_equal(param_type, call_param_types[i]))
+					break;
+			}
+			if (i >= call_param_types.size()) (*error_count)++;
+		}
+	}
+
+}
+
+/* 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 */
+/******************************/
+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))
+		symbol->candidate_datatypes.push_back(&search_constant_type_c::real_type_name);
+	if (calc_size <= sizeoftype(&search_constant_type_c::real_type_name))
+		symbol->candidate_datatypes.push_back(&search_constant_type_c::lreal_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) {
+	int calc_size;
+
+	calc_size = sizeoftype(symbol);
+	if (calc_size <= sizeoftype(&search_constant_type_c::bool_type_name))
+	        symbol->candidate_datatypes.push_back(&search_constant_type_c::bool_type_name);
+	if (calc_size <= sizeoftype(&search_constant_type_c::byte_type_name))
+		symbol->candidate_datatypes.push_back(&search_constant_type_c::byte_type_name);
+	if (calc_size <= sizeoftype(&search_constant_type_c::word_type_name))
+		symbol->candidate_datatypes.push_back(&search_constant_type_c::word_type_name);
+	if (calc_size <= sizeoftype(&search_constant_type_c::dword_type_name))
+		symbol->candidate_datatypes.push_back(&search_constant_type_c::dword_type_name);
+	if (calc_size <= sizeoftype(&search_constant_type_c::lword_type_name))
+		symbol->candidate_datatypes.push_back(&search_constant_type_c::lword_type_name);
+
+	if (calc_size < sizeoftype(&search_constant_type_c::sint_type_name))
+		symbol->candidate_datatypes.push_back(&search_constant_type_c::sint_type_name);
+	if (calc_size < sizeoftype(&search_constant_type_c::int_type_name))
+		symbol->candidate_datatypes.push_back(&search_constant_type_c::int_type_name);
+	if (calc_size < sizeoftype(&search_constant_type_c::dint_type_name))
+		symbol->candidate_datatypes.push_back(&search_constant_type_c::dint_type_name);
+	if (calc_size < sizeoftype(&search_constant_type_c::lint_type_name))
+		symbol->candidate_datatypes.push_back(&search_constant_type_c::lint_type_name);
+	if (calc_size <= sizeoftype(&search_constant_type_c::usint_type_name))
+		symbol->candidate_datatypes.push_back(&search_constant_type_c::usint_type_name);
+	if (calc_size <= sizeoftype(&search_constant_type_c::uint_type_name))
+		symbol->candidate_datatypes.push_back(&search_constant_type_c::uint_type_name);
+	if (calc_size <= sizeoftype(&search_constant_type_c::udint_type_name))
+		symbol->candidate_datatypes.push_back(&search_constant_type_c::udint_type_name);
+	if (calc_size <= sizeoftype(&search_constant_type_c::ulint_type_name))
+		symbol->candidate_datatypes.push_back(&search_constant_type_c::ulint_type_name);
+	if (debug) std::cout << "ANY_INT [" << symbol->candidate_datatypes.size()<< "]" << std::endl;
+	return NULL;
+}
+
+void *fill_candidate_datatypes_c::visit(neg_real_c *symbol) {
+	if (sizeoftype(symbol) <= sizeoftype(&search_constant_type_c::real_type_name))
+		symbol->candidate_datatypes.push_back(&search_constant_type_c::real_type_name);
+	symbol->candidate_datatypes.push_back(&search_constant_type_c::lreal_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))
+		symbol->candidate_datatypes.push_back(&search_constant_type_c::int_type_name);
+	if (calc_size <= sizeoftype(&search_constant_type_c::sint_type_name))
+		symbol->candidate_datatypes.push_back(&search_constant_type_c::sint_type_name);
+	if (calc_size <= sizeoftype(&search_constant_type_c::dint_type_name))
+		symbol->candidate_datatypes.push_back(&search_constant_type_c::dint_type_name);
+	if (calc_size <= sizeoftype(&search_constant_type_c::lint_type_name))
+		symbol->candidate_datatypes.push_back(&search_constant_type_c::lint_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) {
+	int calc_size;
+
+	calc_size = sizeoftype(symbol);
+	if (calc_size <= sizeoftype(&search_constant_type_c::bool_type_name))
+	        symbol->candidate_datatypes.push_back(&search_constant_type_c::bool_type_name);
+	if (calc_size <= sizeoftype(&search_constant_type_c::byte_type_name))
+		symbol->candidate_datatypes.push_back(&search_constant_type_c::byte_type_name);
+	if (calc_size <= sizeoftype(&search_constant_type_c::word_type_name))
+		symbol->candidate_datatypes.push_back(&search_constant_type_c::word_type_name);
+	if (calc_size <= sizeoftype(&search_constant_type_c::dword_type_name))
+		symbol->candidate_datatypes.push_back(&search_constant_type_c::dword_type_name);
+	if (calc_size <= sizeoftype(&search_constant_type_c::lword_type_name))
+		symbol->candidate_datatypes.push_back(&search_constant_type_c::lword_type_name);
+	
+	if (calc_size < sizeoftype(&search_constant_type_c::sint_type_name))
+		symbol->candidate_datatypes.push_back(&search_constant_type_c::sint_type_name);
+	if (calc_size < sizeoftype(&search_constant_type_c::int_type_name))
+		symbol->candidate_datatypes.push_back(&search_constant_type_c::int_type_name);
+	if (calc_size < sizeoftype(&search_constant_type_c::dint_type_name))
+		symbol->candidate_datatypes.push_back(&search_constant_type_c::dint_type_name);
+	if (calc_size < sizeoftype(&search_constant_type_c::lint_type_name))
+		symbol->candidate_datatypes.push_back(&search_constant_type_c::lint_type_name);
+	if (calc_size <= sizeoftype(&search_constant_type_c::usint_type_name))
+		symbol->candidate_datatypes.push_back(&search_constant_type_c::usint_type_name);
+	if (calc_size <= sizeoftype(&search_constant_type_c::uint_type_name))
+		symbol->candidate_datatypes.push_back(&search_constant_type_c::uint_type_name);
+	if (calc_size <= sizeoftype(&search_constant_type_c::udint_type_name))
+		symbol->candidate_datatypes.push_back(&search_constant_type_c::udint_type_name);
+	if (calc_size <= sizeoftype(&search_constant_type_c::ulint_type_name))
+		symbol->candidate_datatypes.push_back(&search_constant_type_c::ulint_type_name);
+	if (debug) std::cout << "ANY_INT [" << symbol->candidate_datatypes.size()<< "]" << std::endl;
+	return NULL;
+}
+
+void *fill_candidate_datatypes_c::visit(octal_integer_c *symbol) {
+	int calc_size;
+
+	calc_size = sizeoftype(symbol);
+	if (calc_size <= sizeoftype(&search_constant_type_c::bool_type_name))
+	        symbol->candidate_datatypes.push_back(&search_constant_type_c::bool_type_name);
+	if (calc_size <= sizeoftype(&search_constant_type_c::byte_type_name))
+		symbol->candidate_datatypes.push_back(&search_constant_type_c::byte_type_name);
+	if (calc_size <= sizeoftype(&search_constant_type_c::word_type_name))
+		symbol->candidate_datatypes.push_back(&search_constant_type_c::word_type_name);
+	if (calc_size <= sizeoftype(&search_constant_type_c::dword_type_name))
+		symbol->candidate_datatypes.push_back(&search_constant_type_c::dword_type_name);
+	if (calc_size <= sizeoftype(&search_constant_type_c::lword_type_name))
+		symbol->candidate_datatypes.push_back(&search_constant_type_c::lword_type_name);
+
+	if (calc_size < sizeoftype(&search_constant_type_c::sint_type_name))
+		symbol->candidate_datatypes.push_back(&search_constant_type_c::sint_type_name);
+	if (calc_size < sizeoftype(&search_constant_type_c::int_type_name))
+		symbol->candidate_datatypes.push_back(&search_constant_type_c::int_type_name);
+	if (calc_size < sizeoftype(&search_constant_type_c::dint_type_name))
+		symbol->candidate_datatypes.push_back(&search_constant_type_c::dint_type_name);
+	if (calc_size < sizeoftype(&search_constant_type_c::lint_type_name))
+		symbol->candidate_datatypes.push_back(&search_constant_type_c::lint_type_name);
+	if (calc_size <= sizeoftype(&search_constant_type_c::usint_type_name))
+		symbol->candidate_datatypes.push_back(&search_constant_type_c::usint_type_name);
+	if (calc_size <= sizeoftype(&search_constant_type_c::uint_type_name))
+		symbol->candidate_datatypes.push_back(&search_constant_type_c::uint_type_name);
+	if (calc_size <= sizeoftype(&search_constant_type_c::udint_type_name))
+		symbol->candidate_datatypes.push_back(&search_constant_type_c::udint_type_name);
+	if (calc_size <= sizeoftype(&search_constant_type_c::ulint_type_name))
+		symbol->candidate_datatypes.push_back(&search_constant_type_c::ulint_type_name);
+	if (debug) std::cout << "ANY_INT [" << symbol->candidate_datatypes.size()<< "]" << std::endl;
+	return NULL;
+}
+
+void *fill_candidate_datatypes_c::visit(hex_integer_c *symbol) {
+	int calc_size;
+
+	calc_size = sizeoftype(symbol);
+	if (calc_size <= sizeoftype(&search_constant_type_c::bool_type_name))
+	        symbol->candidate_datatypes.push_back(&search_constant_type_c::bool_type_name);
+	if (calc_size <= sizeoftype(&search_constant_type_c::byte_type_name))
+		symbol->candidate_datatypes.push_back(&search_constant_type_c::byte_type_name);
+	if (calc_size <= sizeoftype(&search_constant_type_c::word_type_name))
+		symbol->candidate_datatypes.push_back(&search_constant_type_c::word_type_name);
+	if (calc_size <= sizeoftype(&search_constant_type_c::dword_type_name))
+		symbol->candidate_datatypes.push_back(&search_constant_type_c::dword_type_name);
+	if (calc_size <= sizeoftype(&search_constant_type_c::lword_type_name))
+		symbol->candidate_datatypes.push_back(&search_constant_type_c::lword_type_name);
+
+	if (calc_size < sizeoftype(&search_constant_type_c::sint_type_name))
+		symbol->candidate_datatypes.push_back(&search_constant_type_c::sint_type_name);
+	if (calc_size < sizeoftype(&search_constant_type_c::int_type_name))
+		symbol->candidate_datatypes.push_back(&search_constant_type_c::int_type_name);
+	if (calc_size < sizeoftype(&search_constant_type_c::dint_type_name))
+		symbol->candidate_datatypes.push_back(&search_constant_type_c::dint_type_name);
+	if (calc_size < sizeoftype(&search_constant_type_c::lint_type_name))
+		symbol->candidate_datatypes.push_back(&search_constant_type_c::lint_type_name);
+	if (calc_size <= sizeoftype(&search_constant_type_c::usint_type_name))
+		symbol->candidate_datatypes.push_back(&search_constant_type_c::usint_type_name);
+	if (calc_size <= sizeoftype(&search_constant_type_c::uint_type_name))
+		symbol->candidate_datatypes.push_back(&search_constant_type_c::uint_type_name);
+	if (calc_size <= sizeoftype(&search_constant_type_c::udint_type_name))
+		symbol->candidate_datatypes.push_back(&search_constant_type_c::udint_type_name);
+	if (calc_size <= sizeoftype(&search_constant_type_c::ulint_type_name))
+		symbol->candidate_datatypes.push_back(&search_constant_type_c::ulint_type_name);
+	if (debug) std::cout << "ANY_INT [" << symbol->candidate_datatypes.size()<< "]" << std::endl;
+	return NULL;
+}
+
+void *fill_candidate_datatypes_c::visit(integer_literal_c *symbol) {
+	symbol->candidate_datatypes.push_back(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->candidate_datatypes.push_back(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->candidate_datatypes.push_back(symbol->type);
+	return NULL;
+}
+
+void *fill_candidate_datatypes_c::visit(boolean_literal_c *symbol) {
+	symbol->candidate_datatypes.push_back(&search_constant_type_c::bool_type_name);
+	return NULL;
+}
+
+void *fill_candidate_datatypes_c::visit(boolean_true_c *symbol) {
+	symbol->candidate_datatypes.push_back(&search_constant_type_c::bool_type_name);
+	return NULL;
+}
+
+void *fill_candidate_datatypes_c::visit(boolean_false_c *symbol) {
+	symbol->candidate_datatypes.push_back(&search_constant_type_c::bool_type_name);
+	return NULL;
+}
+
+/*******************************/
+/* B.1.2.2   Character Strings */
+/*******************************/
+void *fill_candidate_datatypes_c::visit(double_byte_character_string_c *symbol) {
+	symbol->candidate_datatypes.push_back(&search_constant_type_c::wstring_type_name);
+	return NULL;
+}
+
+void *fill_candidate_datatypes_c::visit(single_byte_character_string_c *symbol) {
+	symbol->candidate_datatypes.push_back(&search_constant_type_c::string_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) {
+	symbol->candidate_datatypes.push_back(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) {
+	symbol->candidate_datatypes.push_back(symbol->type_name);
+	return NULL;
+}
+
+void *fill_candidate_datatypes_c::visit(date_c *symbol) {
+	symbol->candidate_datatypes.push_back(symbol->type_name);
+	return NULL;
+}
+
+void *fill_candidate_datatypes_c::visit(date_and_time_c *symbol) {
+	symbol->candidate_datatypes.push_back(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]))
+				symbol->candidate_datatypes.push_back(symbol->lower_limit->candidate_datatypes[l]);
+		}
+	}
+	return NULL;
+}
+
+
+void *fill_candidate_datatypes_c::visit(data_type_declaration_c *symbol) {
+	// TODO !!!
+	/* for the moment we must return NULL so semantic analysis of remaining code is not interrupted! */
+	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)
+		symbol->candidate_datatypes.push_back(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)
+		symbol->candidate_datatypes.push_back(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
+		symbol->candidate_datatypes.push_back(&search_constant_type_c::bool_type_name);
+		break;
+
+	case 'B': // byte - 8 bits
+		symbol->candidate_datatypes.push_back(&search_constant_type_c::byte_type_name);
+		break;
+
+	case 'W': // word - 16 bits
+		symbol->candidate_datatypes.push_back(&search_constant_type_c::word_type_name);
+		break;
+
+	case 'D': // double word - 32 bits
+		symbol->candidate_datatypes.push_back(&search_constant_type_c::dword_type_name);
+		break;
+
+	case 'L': // long word - 64 bits
+		symbol->candidate_datatypes.push_back(&search_constant_type_c::lword_type_name);
+		break;
+
+	default:  // if none of the above, then the empty string was used <=> boolean
+		symbol->candidate_datatypes.push_back(&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) symbol->candidate_datatypes.push_back(result);
+	
+	/* recursively call the subscript list, so we can check the data types of the expressions used for the subscripts */
+if (debug) std::cout << "ARRAY_VAR XXX\n";		
+	symbol->subscript_list->accept(*this);
+if (debug) std::cout << "ARRAY_VAR YYY\n";		
+
+	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... */
+#if 0
+void *fill_candidate_datatypes_c::visit(subscript_list_c *symbol) {
+}
+#endif
+
+
+/*  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) symbol->candidate_datatypes.push_back(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;
+	prev_il_instruction = NULL;
+	symbol->function_body->accept(*this);
+	prev_il_instruction = NULL;
+	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;
+	prev_il_instruction = NULL;
+	symbol->fblock_body->accept(*this);
+	prev_il_instruction = NULL;
+	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;
+	prev_il_instruction = NULL;
+	symbol->function_block_body->accept(*this);
+	prev_il_instruction = NULL;
+	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) {
+#if 0
+	// TODO !!!
+	/* for the moment we must return NULL so semantic analysis of remaining code is not interrupted! */
+#endif
+	return NULL;
+}
+
+/****************************************/
+/* B.2 - Language IL (Instruction List) */
+/****************************************/
+/***********************************/
+/* B 2.1 Instructions and Operands */
+/***********************************/
+// void *visit(instruction_list_c *symbol);
+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;
+	return NULL;
+}
+
+void *fill_candidate_datatypes_c::visit(il_function_call_c *symbol) {
+}
+
+/* MJS: Manuele, could you please not delete the following 2 lines of comments. They help me understand where this class is used
+ *     and when it is created by bison - syntax parse, and how it can show up in the abstract syntax tree.
+ *
+ *       Actually, it could be helpful if we could have all the similar comments already present in visit_expression_type_c
+ *       in the 3 new classes fill/narrow/print candidate datatype 
+ */
+/* | 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) {
+  if (NULL != symbol->il_operand)
+    symbol->il_operand->accept(*this);
+  
+  il_parenthesis_level++;
+
+  /* Note that prev_il_instruction will actually be used to get the current value store in the il_default_variable */
+  /* If a symbol->il_operand is provided, then that will be the result before executing the simple_instr_list.
+   * If this symbol is NULL, then the current result is also NULL, which is correct for what we want to do!
+   */
+  symbol_c *prev_il_instruction_backup = prev_il_instruction;
+  prev_il_instruction = symbol->il_operand;
+  
+  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 = prev_il_instruction;
+  prev_il_instruction = prev_il_instruction_backup;
+  symbol->il_expr_operator->accept(*this);
+  il_operand = NULL;
+  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;
+  return NULL;
+}
+
+void *fill_candidate_datatypes_c::visit(il_fb_call_c *symbol) {
+}
+
+void *fill_candidate_datatypes_c::visit(il_formal_funct_call_c *symbol) {
+
+}
+
+/*
+    void *visit(il_operand_list_c *symbol);
+    void *visit(simple_instr_list_c *symbol);
+    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++) {
+		symbol->candidate_datatypes.push_back(il_operand->candidate_datatypes[i]);
+	}
+	if (debug) std::cout << "LD [" <<  il_operand->candidate_datatypes.size() << "] ==> "  << symbol->candidate_datatypes.size() << " result.\n";
+	prev_il_instruction = symbol;
+	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]))
+			symbol->candidate_datatypes.push_back(il_operand->candidate_datatypes[i]);
+	}
+	if (debug) std::cout << "LDN [" << il_operand->candidate_datatypes.size() << "] ==> "  << symbol->candidate_datatypes.size() << " result.\n";
+	prev_il_instruction = symbol;
+	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))
+				symbol->candidate_datatypes.push_back(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";
+	prev_il_instruction = symbol;
+	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(il_operand->candidate_datatypes[i]))
+				symbol->candidate_datatypes.push_back(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";
+	prev_il_instruction = symbol;
+	return NULL;
+}
+
+void *fill_candidate_datatypes_c::visit(NOT_operator_c *symbol) {
+	prev_il_instruction = symbol;
+	return NULL;
+}
+
+void *fill_candidate_datatypes_c::visit(S_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_BOOL_compatible(il_operand->candidate_datatypes[i]))
+				symbol->candidate_datatypes.push_back(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";
+	prev_il_instruction = symbol;
+	return NULL;
+}
+
+void *fill_candidate_datatypes_c::visit(R_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_BOOL_compatible(il_operand->candidate_datatypes[i]))
+				symbol->candidate_datatypes.push_back(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";
+	prev_il_instruction = symbol;
+	return NULL;
+}
+
+void *fill_candidate_datatypes_c::visit(S1_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_BOOL_compatible(il_operand->candidate_datatypes[i]))
+				symbol->candidate_datatypes.push_back(prev_instruction_type);
+		}
+	}
+	if (debug) std::cout << "S1 [" << prev_il_instruction->candidate_datatypes.size() << "," << il_operand->candidate_datatypes.size() << "] ==> "  << symbol->candidate_datatypes.size() << " result.\n";
+	prev_il_instruction = symbol;
+	return NULL;
+}
+
+void *fill_candidate_datatypes_c::visit(R1_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_BOOL_compatible(il_operand->candidate_datatypes[i]))
+				symbol->candidate_datatypes.push_back(prev_instruction_type);
+		}
+	}
+	if (debug) std::cout << "R1 [" << prev_il_instruction->candidate_datatypes.size() << "," << il_operand->candidate_datatypes.size() << "] ==> "  << symbol->candidate_datatypes.size() << " result.\n";
+	prev_il_instruction = symbol;
+	return NULL;
+}
+
+void *fill_candidate_datatypes_c::visit(CLK_operator_c *symbol) {
+	/* MANU:
+	 * How it works? I(MANU) don't know this function
+	 */
+	prev_il_instruction = symbol;
+	return NULL;
+}
+
+void *fill_candidate_datatypes_c::visit(CU_operator_c *symbol) {
+	/* MANU:
+	 * How it works? I(MANU) don't know this function
+	 */
+	prev_il_instruction = symbol;
+	return NULL;
+}
+
+void *fill_candidate_datatypes_c::visit(CD_operator_c *symbol) {
+	/* MANU:
+	 * How it works? I(MANU) don't know this function
+	 */
+
+	prev_il_instruction = symbol;
+	return NULL;
+}
+
+void *fill_candidate_datatypes_c::visit(PV_operator_c *symbol) {
+	/* MANU:
+	 * How it works? I(MANU) don't know this function
+	 */
+
+	prev_il_instruction = symbol;
+	return NULL;
+}
+
+void *fill_candidate_datatypes_c::visit(IN_operator_c *symbol) {
+	/* MANU:
+	 * How it works? I(MANU) don't know this function
+	 */
+
+	prev_il_instruction = symbol;
+	return NULL;
+}
+
+void *fill_candidate_datatypes_c::visit(PT_operator_c *symbol) {
+	/* MANU:
+	 * How it works? I(MANU) don't know this function
+	 */
+
+	prev_il_instruction = symbol;
+	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))
+				symbol->candidate_datatypes.push_back(prev_instruction_type);
+		}
+	}
+	prev_il_instruction = symbol;
+	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))
+				symbol->candidate_datatypes.push_back(prev_instruction_type);
+		}
+	}
+	prev_il_instruction = symbol;
+	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))
+				symbol->candidate_datatypes.push_back(prev_instruction_type);
+		}
+	}
+	prev_il_instruction = symbol;
+	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))
+				symbol->candidate_datatypes.push_back(prev_instruction_type);
+		}
+	}
+	prev_il_instruction = symbol;
+	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))
+				symbol->candidate_datatypes.push_back(prev_instruction_type);
+		}
+	}
+	prev_il_instruction = symbol;
+	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))
+				symbol->candidate_datatypes.push_back(prev_instruction_type);
+		}
+	}
+	prev_il_instruction = symbol;
+	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))
+				symbol->candidate_datatypes.push_back(prev_instruction_type);
+			else {
+				symbol_c *result = widening_conversion(prev_instruction_type, operand_type, widen_ADD_table);
+				if (result)
+					symbol->candidate_datatypes.push_back(result);
+
+			}
+		}
+	}
+	if (debug) std::cout <<  "ADD [" << prev_il_instruction->candidate_datatypes.size() << "," << il_operand->candidate_datatypes.size() << "] ==> "  << symbol->candidate_datatypes.size() << " result.\n";
+	prev_il_instruction = symbol;
+	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))
+				symbol->candidate_datatypes.push_back(prev_instruction_type);
+			else {
+				symbol_c *result = widening_conversion(prev_instruction_type, operand_type, widen_SUB_table);
+				if (result)
+					symbol->candidate_datatypes.push_back(result);
+			}
+		}
+	}
+	if (debug) std::cout <<  "SUB [" << prev_il_instruction->candidate_datatypes.size() << "," << il_operand->candidate_datatypes.size() << "] ==> "  << symbol->candidate_datatypes.size() << " result.\n";
+	prev_il_instruction = symbol;
+	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))
+				symbol->candidate_datatypes.push_back(prev_instruction_type);
+			else {
+				symbol_c *result = widening_conversion(prev_instruction_type, operand_type, widen_MUL_table);
+				if (result)
+					symbol->candidate_datatypes.push_back(result);
+			}
+		}
+	}
+	if (debug) std::cout <<  "MUL [" << prev_il_instruction->candidate_datatypes.size() << "," << il_operand->candidate_datatypes.size() << "] ==> "  << symbol->candidate_datatypes.size() << " result.\n";
+	prev_il_instruction = symbol;
+	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))
+				symbol->candidate_datatypes.push_back(prev_instruction_type);
+			else {
+				symbol_c *result = widening_conversion(prev_instruction_type, operand_type, widen_DIV_table);
+				if (result)
+					symbol->candidate_datatypes.push_back(result);
+			}
+		}
+	}
+	if (debug) std::cout <<  "DIV [" << prev_il_instruction->candidate_datatypes.size() << "," << il_operand->candidate_datatypes.size() << "] ==> "  << symbol->candidate_datatypes.size() << " result.\n";
+	prev_il_instruction = symbol;
+	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))
+				symbol->candidate_datatypes.push_back(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";
+	prev_il_instruction = symbol;
+	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) symbol->candidate_datatypes.push_back(&search_constant_type_c::bool_type_name);
+	prev_il_instruction = symbol;
+	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) symbol->candidate_datatypes.push_back(&search_constant_type_c::bool_type_name);
+	prev_il_instruction = symbol;
+	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) symbol->candidate_datatypes.push_back(&search_constant_type_c::bool_type_name);
+	prev_il_instruction = symbol;
+	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) symbol->candidate_datatypes.push_back(&search_constant_type_c::bool_type_name);
+	prev_il_instruction = symbol;
+	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) symbol->candidate_datatypes.push_back(&search_constant_type_c::bool_type_name);
+	prev_il_instruction = symbol;
+	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) symbol->candidate_datatypes.push_back(&search_constant_type_c::bool_type_name);
+	prev_il_instruction = symbol;
+	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 !! */
+		symbol->candidate_datatypes.push_back(prev_il_instruction->candidate_datatypes[i]);
+	}
+	if (debug) std::cout <<  "CAL [" << prev_il_instruction->candidate_datatypes.size() << "] ==> "  << symbol->candidate_datatypes.size() << " result.\n";
+	prev_il_instruction = symbol;
+	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_type(prev_il_instruction->candidate_datatypes[i], bool_type_name_c))
+			symbol->candidate_datatypes.push_back(prev_il_instruction->candidate_datatypes[i]);
+	}
+	if (debug) std::cout <<  "CALC [" << prev_il_instruction->candidate_datatypes.size() << "] ==> "  << symbol->candidate_datatypes.size() << " result.\n";
+	prev_il_instruction = symbol;
+	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_type(prev_il_instruction->candidate_datatypes[i], bool_type_name_c))
+			symbol->candidate_datatypes.push_back(prev_il_instruction->candidate_datatypes[i]);
+	}
+	if (debug) std::cout <<  "CALCN [" << prev_il_instruction->candidate_datatypes.size() << "] ==> "  << symbol->candidate_datatypes.size() << " result.\n";
+	prev_il_instruction = symbol;
+	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 !! */
+		symbol->candidate_datatypes.push_back(prev_il_instruction->candidate_datatypes[i]);
+	}
+	if (debug) std::cout <<  "RET [" << prev_il_instruction->candidate_datatypes.size() << "] ==> "  << symbol->candidate_datatypes.size() << " result.\n";
+	prev_il_instruction = symbol;
+	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_type(prev_il_instruction->candidate_datatypes[i], bool_type_name_c))
+			symbol->candidate_datatypes.push_back(prev_il_instruction->candidate_datatypes[i]);
+	}
+	if (debug) std::cout <<  "RETC [" << prev_il_instruction->candidate_datatypes.size() << "] ==> "  << symbol->candidate_datatypes.size() << " result.\n";
+	prev_il_instruction = symbol;
+	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_type(prev_il_instruction->candidate_datatypes[i], bool_type_name_c))
+			symbol->candidate_datatypes.push_back(prev_il_instruction->candidate_datatypes[i]);
+	}
+	if (debug) std::cout <<  "RETCN [" << prev_il_instruction->candidate_datatypes.size() << "] ==> "  << symbol->candidate_datatypes.size() << " result.\n";
+	prev_il_instruction = symbol;
+	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 !! */
+		symbol->candidate_datatypes.push_back(prev_il_instruction->candidate_datatypes[i]);
+	}
+	if (debug) std::cout <<  "JMP [" << prev_il_instruction->candidate_datatypes.size() << "] ==> "  << symbol->candidate_datatypes.size() << " result.\n";
+	prev_il_instruction = symbol;
+	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_type(prev_il_instruction->candidate_datatypes[i], bool_type_name_c))
+			symbol->candidate_datatypes.push_back(prev_il_instruction->candidate_datatypes[i]);
+	}
+	if (debug) std::cout <<  "JMPC [" << prev_il_instruction->candidate_datatypes.size() << "] ==> "  << symbol->candidate_datatypes.size() << " result.\n";
+	prev_il_instruction = symbol;
+	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_type(prev_il_instruction->candidate_datatypes[i], bool_type_name_c))
+			symbol->candidate_datatypes.push_back(prev_il_instruction->candidate_datatypes[i]);
+	}
+	if (debug) std::cout <<  "JMPCN [" << prev_il_instruction->candidate_datatypes.size() << "] ==> "  << symbol->candidate_datatypes.size() << " result.\n";
+	prev_il_instruction = symbol;
+	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]))
+				symbol->candidate_datatypes.push_back(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]))
+				symbol->candidate_datatypes.push_back(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]))
+				symbol->candidate_datatypes.push_back(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) symbol->candidate_datatypes.push_back(&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)
+		symbol->candidate_datatypes.push_back(&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)
+		symbol->candidate_datatypes.push_back(&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)
+		symbol->candidate_datatypes.push_back(&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)
+		symbol->candidate_datatypes.push_back(&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)
+		symbol->candidate_datatypes.push_back(&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))
+				symbol->candidate_datatypes.push_back(left_type);
+			else {
+				symbol_c *result = widening_conversion(left_type, right_type, widen_ADD_table);
+				if (result)
+					symbol->candidate_datatypes.push_back(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))
+				symbol->candidate_datatypes.push_back(left_type);
+			else {
+				symbol_c *result = widening_conversion(left_type, right_type, widen_SUB_table);
+				if (result)
+					symbol->candidate_datatypes.push_back(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))
+				symbol->candidate_datatypes.push_back(left_type);
+			else {
+				symbol_c *result = widening_conversion(left_type, right_type, widen_MUL_table);
+				if (result)
+					symbol->candidate_datatypes.push_back(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))
+				symbol->candidate_datatypes.push_back(left_type);
+			else {
+				symbol_c *result = widening_conversion(left_type, right_type, widen_DIV_table);
+				if (result)
+					symbol->candidate_datatypes.push_back(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))
+				symbol->candidate_datatypes.push_back(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++) {
+		symbol->candidate_datatypes.push_back(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) {
+	symbol->exp->accept(*this);
+	for (unsigned int i = 0; i < symbol->exp->candidate_datatypes.size(); i++) {
+		if (is_ANY_MAGNITUDE_compatible(symbol->exp->candidate_datatypes[i]))
+			symbol->candidate_datatypes.push_back(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]))
+			symbol->candidate_datatypes.push_back(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) {
+	function_declaration_c *f_decl;
+	list_c *parameter_list;
+	list_c *parameter_candidate_datatypes;
+	symbol_c *parameter_type;
+	int error_count;
+	function_symtable_t::iterator lower = function_symtable.lower_bound(symbol->function_name);
+	function_symtable_t::iterator upper = function_symtable.upper_bound(symbol->function_name);
+
+	if (NULL != symbol->formal_param_list)
+		parameter_list = (list_c *)symbol->formal_param_list;
+	else if (NULL != symbol->nonformal_param_list)
+		parameter_list = (list_c *)symbol->nonformal_param_list;
+	else ERROR;
+	if (debug) std::cout << "function()\n";
+	parameter_list->accept(*this);
+	for(; lower != upper; lower++) {
+		f_decl = function_symtable.get_value(lower);
+		error_count = 0;
+		/* Check if function declaration in symbol_table is compatible with parameters */
+		if (NULL != symbol->nonformal_param_list)
+			/* nonformal parameter function call */
+			match_nonformal_call(symbol, f_decl, &error_count);
+		else
+			/* formal parameter function call */
+			match_formal_call (symbol, f_decl, &error_count);
+		if (0 == error_count) {
+			/* Add basetype matching function only if not present */
+			unsigned int k;
+			parameter_type = base_type(f_decl->type_name);
+			for(k = 0; k < symbol->candidate_datatypes.size(); k++) {
+				if (is_type_equal(parameter_type, symbol->candidate_datatypes[k]))
+					break;
+			}
+			if (k >= symbol->candidate_datatypes.size())
+				symbol->candidate_datatypes.push_back(parameter_type);
+		}
+	}
+	if (debug) std::cout << "end_function() [" << 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))
+				symbol->candidate_datatypes.push_back(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 3.2.3 Selection Statements */
+/********************************/
+void *fill_candidate_datatypes_c::visit(if_statement_c *symbol) {
+	/* MANU:
+	 * IF statement accept only BOOL type. We intersect with BOOL type to validate current if condition
+	 * Example:
+	 * IF 1 THEN 		---> 	 ok
+	 * IF 5 THEN 		---> not ok
+	 * IF 1 OR 1 THEN	--->     ok
+	 * IF 1 OR 5 THEN   ---> not ok
+	 * IF SHL() THEN	---> 	 ok if shl return BOOL
+	 * IF INT_TO_REAL() ---> not ok
+	 */
+	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;
+}
+
+
+
+
+
+