Thread: Problem with Program to Check if Separators Match

You can switch on a single character, not a string. You can't use strcmp on a string, you use ==.

Originally Posted by tabstop

You can switch on a single character, not a string. You can't use strcmp on a string, you use ==.

Okay...so I created a new variable, a character, which I am initializing to the same thing as ch, which is lineToCheck[j], and running my switch on that. Also, I uncommented the other if statement that I had, which uses == instead of strcmp, but now I get these errors that make it seem like I can't use == either. So I don't know what to do now.

Thanks for all the help, tabstop!

Here are the errors I am getting now:
MatchChecker.h|21|warning: comparison between signed and unsigned integer expressions|
MatchChecker.h|23|error: invalid conversion from `char' to `const char*'|
MatchChecker.h|23|error: initializing argument 1 of `std::basic_string<_CharT, _Traits, _Alloc>::basic_string(const _CharT*, const _Alloc&) [with _CharT = char, _Traits = std::char_traits<char>, _Alloc = std::allocator<char>]'|
MatchChecker.h|37|error: conversion from `void' to non-scalar type `std::basic_string<char, std::char_traits<char>, std::allocator<char> >' requested|
MatchChecker.h|40|error: no match for 'operator==' in 'ch == '}''|
MatchChecker.h|40|error: no match for 'operator==' in 'popper == '{''|
MatchChecker.h|40|error: no match for 'operator==' in 'ch == ']''|
MatchChecker.h|40|error: no match for 'operator==' in 'popper == '[''|
MatchChecker.h|40|error: no match for 'operator==' in 'ch == ')''|
MatchChecker.h|40|error: no match for 'operator==' in 'popper == '(''|
MatchChecker.h|42|error: no match for 'operator+' in 'std:: operator+(const std::basic_string<_CharT, _Traits, _Alloc>&, const _CharT*) [with _CharT = char, _Traits = std::char_traits<char>, _Alloc = std::allocator<char>](((const char*)" at the position ")) + j'|
MatchChecker.h|48|error: no match for 'operator+' in 'std:: operator+(const std::basic_string<_CharT, _Traits, _Alloc>&, const _CharT*) [with _CharT = char, _Traits = std::char_traits<char>, _Alloc = std::allocator<char>](((const char*)" at the position ")) + j'|


And here is my code:

Code:

#include <stdio.h>
#include <sstream>
#include <string>
#include <stdexcept>
#include <stack>

// protections
#ifndef MatchChecker_H
#define MatchChecker_H

using namespace std;

class MatchChecker
{

      public:
      static string matchChecker(string lineToCheck)
      {
             stack<string> myStack;

             for (int j = 0; j < lineToCheck.length(); j++) // line 20
             {
                 string ch = lineToCheck[j];
                 char switchValue = lineToCheck[j];
                 switch (switchValue)
                 {
                        case '{':
                        case '[':
                        case '(':
                             myStack.push(ch);
                             break;
                        case '}':
                        case ']':
                        case ')':
                             if (!myStack.empty())
                             {
                                string popper = myStack.pop();

                                 //if (((strcmp (ch, '{') == 0) && (strcmp (popper, '}') == 0)) || ((strcmp (ch, '[') == 0) && (strcmp (popper, ']') == 0)) || ((strcmp (ch, '(') == 0) && (strcmp (popper, ')') == 0)))
                                 if (((ch == '}') && popper == '{') || ((ch == ']') && (popper == '[')) || ((ch == ')') && (popper == '(')))
                                    {
                                    string returnValue = "Error: " + ch + " at the position " + j + " does not match";
                                    return returnValue;
                                    }
                             }
                             else
                             {
                                 string returnValue = "Error: " + ch + " at the position " + j + " does not match";
                                 return returnValue;
                             }
                             break;
                        default:
                             break;
                 }
             }
             if (!myStack.empty())
             {
             return ("Error: missing right delimiter");
             }
      }
};

#endif

Alright, I changed my single quote marks to doubles, so that the characters were being read as strings, and now I am not getting those errors about the == operator. I am still getting the errors about the + operator, though, so I am unsure about how to concatenate the strings that I have now. How do I do that?

Also, I am still getting that error about my pop function. What in the world is going on with that? Is there something I have done wrong that is making it do this?

Thank you for all of the help!!

Here are the errors I am still getting:
MatchChecker.h|21|warning: comparison between signed and unsigned integer expressions|
MatchChecker.h|23|error: invalid conversion from `char' to `const char*'|
MatchChecker.h|23|error: initializing argument 1 of `std::basic_string<_CharT, _Traits, _Alloc>::basic_string(const _CharT*, const _Alloc&) [with _CharT = char, _Traits = std::char_traits<char>, _Alloc = std::allocator<char>]'|
MatchChecker.h|37|error: conversion from `void' to non-scalar type `std::basic_string<char, std::char_traits<char>, std::allocator<char> >' requested|
MatchChecker.h|42|error: no match for 'operator+' in 'std:: operator+(const std::basic_string<_CharT, _Traits, _Alloc>&, const _CharT*) [with _CharT = char, _Traits = std::char_traits<char>, _Alloc = std::allocator<char>](((const char*)" at the position ")) + j'|
MatchChecker.h|48|error: no match for 'operator+' in 'std:: operator+(const std::basic_string<_CharT, _Traits, _Alloc>&, const _CharT*) [with _CharT = char, _Traits = std::char_traits<char>, _Alloc = std::allocator<char>](((const char*)" at the position ")) + j'|