static int literal_terminator_char(int inputChar) {
return inputChar==EOF || character_is_break_out_token(inputChar) ||
is_whitespace(inputChar) ||
is_paren(inputChar) ||
is_quotation(inputChar);
}
int ExpressionManager::get_precedence(char op){
int paren_type = is_paren(op);
if(paren_type != NOT_A_PAREN){
//then it is a paren
return paren_type;
}
//otherwise it is an op
char op_str[1];
op_str[0] = op;
op_str[1] = '\0';
int index = strcspn(operators, op_str);
return op_precedence[index];
}
string ExpressionManager::infixToPostfix(string infixExpression){
stack<char> symbols;
string out_str = "";
//do tests for the validity of the infix expression
if(!isBalanced(infixExpression)){
return invalid;
}
if(!op_num_ratio_check(infixExpression)){
return invalid;
}
char exp_str[STR_BUFF_SIZE];
exp_str[0] = '\0';
//create a C string from the expression string
//for use in strtok
strcat(exp_str, infixExpression.c_str());
char * token;
//use strtok to tokenize the string
//separating by spaces
token = strtok(exp_str, " ");
while( 1 ){
if(token == NULL){
while(!symbols.empty()){
out_str += symbols.top();
out_str += " ";
symbols.pop();
}
break;
}
//cout << "token: " << token << "\n";
if(is_int_num(string(token))){
out_str += string(token);
out_str += " ";
} else if(is_paren( *token ) == OPEN_PAREN){
symbols.push( *token );
} else if(is_paren( *token ) == CLOSE_PAREN){
char top_char = symbols.top();
symbols.pop();
while(get_precedence(top_char) > OPEN_PAREN){
//symbols.pop();
out_str += top_char;
out_str += " ";
top_char = symbols.top();
symbols.pop();
}
} else if(is_op( *token )){
if(symbols.empty()){
symbols.push( *token );
} else {
char top_char = symbols.top();
int top_prec = get_precedence(top_char);
int token_prec = get_precedence( *token );
while( top_prec >= token_prec ){
//go through any tokens with greater than or equal precedence
symbols.pop();
out_str += top_char;
out_str += " ";
if(symbols.empty()){
break;
}
top_char = symbols.top();
top_prec = get_precedence(top_char);
}
symbols.push( *token );
}
}
//increment to the next token
token = strtok(NULL, " ");
}
//to remove the last part of the string (the trailing space)
//if using C++11 you can do out_str.pop_back();
out_str.erase(out_str.end() - 1);
return out_str;
}
