Thread: Palindromes

Originally Posted by jewelz

hmm..getting a compilation error..it's saying:

error: expected identifier before '(' token

indicating the line with while (cin >> s)

You need to surround the entire condition (both checks and the &&) inside one big set of parentheses.

Ok now on to fix the problem that I have been having since completing the first part of the assignment (output just palindromes)...the compiler is telling me:

pal.h:4: error: 'string' in namespace 'std' does not name a type
pal.h:5: error: 'string' is not a member of 'std'
pal.h:5: error: 's' was not declared in this scope

and its saying that i cant use the isPalindrome function:

error: 'isPalindrome' cannot be used as a function

if u guys need to look at my code for header file and implementation file for two functions, it's on the previous pages..

Originally Posted by jewelz

Ok now on to fix the problem that I have been having since completing the first part of the assignment (output just palindromes)...the compiler is telling me:

pal.h:4: error: 'string' in namespace 'std' does not name a type
pal.h:5: error: 'string' is not a member of 'std'
pal.h:5: error: 's' was not declared in this scope

and its saying that i cant use the isPalindrome function:

error: 'isPalindrome' cannot be used as a function

if u guys need to look at my code for header file and implementation file for two functions, it's on the previous pages..

That tells me you don't have #include <string> in your pal.h file (if that file needs string, you have to include <string> in that file).

yeah but one of my classmates said he didn't need to include that in his pal.h and it ran fine..plus i thought header files are generally not supposed to have them anyway?

Originally Posted by jewelz

yeah but one of my classmates said he didn't need to include that in his pal.h and it ran fine..plus i thought header files are generally not supposed to have them anyway?

Then either (a) he is not using strings (surely he's not using char[] gasp horror) or (b) he's including some other file that in its turn includes string.h.

Header files are most certainly supposed to include all the header files needed for its own content to make sense.

well i included the <string> and compiled it again, this time the only problem is that it's saying that there is an undefined reference to 'isPalindrome(std.....)

i dunno what to make of that error.. pal.h is included but idk whats going on..

And is isPalindrome prototyped in pal.h? More importantly, is it prototyped the way it is defined and the way it is called?

here is my code for the entire project:

pal.h

Code:

#ifndef GUARD_PAL_H_
#define GUARD_PAL_H_

#include<string>

std::string reverse(const std::string& s);
bool isPalindrome(const std::string& s);

#endif

implementation file - pal.cc

Code:

#include "pal.h"
#include <cstdlib> 

//function declaration
std::string reverse(const std::string& s)
{
    string s2 = "";
    for (int i = 1; i < s.length(); i++)
	{
	    s2 = s2 + s[s.length() - i];
	}
    s2 = s2 + s[0];
    return s2;
}

bool isPalindrome(const std::string& s)
{
    return(s==reverse(s));

}

main function:

Code:

#include "pal.h"
#include <string>
#include <cstdlib>
#include <iostream>

using std::endl;
using std::string;
using std::cout;
using std::cin;


int main()

{
    typedef string::size_type string_size;
    
    string s;
    string_size max = s.size();
    string longest = s;
    
    while((cin >> s) && (isPalindrome(s)== true)) {
	string_size size = s.size();
	if (size > max) {
	    max = size;
	    longest = s;
	}
    }

    cout << "Longest Palindrome is " << "\"" << longest << "\""
	 << "whose length is " << max << endl;
    
    return 0;
}

there is never a reason to compare a bool to a bool.

Code:

isPalindrome(s)== true

is identical to

Code:

isPalindrome(s)

Oh, so linker error. Make sure pal.cc is in your project, or included in your command-line compilation.

i believe either you changed your code from what's posted above or you have misspoken.

yeah..i made a silly mistake =) anyway thanks for all the help guys..really appreciate it