errors may b concerning strings

[manzoor]

#include <iostream>
#include <string>
using namespace std;

int main()
{
	string letters = "Madam I'm Adam";
	size_t length = letters.length();
	bool isPalindrome;
	unsigned index = 0;
	string testStr;
	
	// Lowercase all the characters
	// extract the letters without including punctuation and spaces
	while (index < length)
	{
		if (isalpha(letters[index]))		
			testStr += tolower(letters[index]);

		index++;
	}

	// Now check if it is a palindrome
	isPalindrome = true;
	for (int i = 0; i < (testStr.length() / 2); i++)
	{
		if (testStr[i] != testStr[testStr.length() - (i-1)])
		{
			isPalindrome = false;
			break;
		}
	}
	cout << "\"" << letters << "\"" << isPalindrome ? "is" : "is not"
		 << " a palindrome." << endl;

	return EXIT_SUCCESS;

}

I can get it to compile due to some errors which I'm unable to understand, I'm compiling it with Visual Studio 2005

The build log is

EDIT:

Got it. Was using C++/CLI so, had forgotten the parenthesis

but still there are two errors

1>------ Build started: Project: C++ConsoleTest, Configuration: Debug Win32 ------
1>Compiling...
1>test.cpp
1>c:\documents and settings\manzoor\my documents\visual studio 2005\projects\c++consoletest\c++consoletest\test.cpp(25) : warning C4018: '<' : signed/unsigned mismatch
1>c:\documents and settings\manzoor\my documents\visual studio 2005\projects\c++consoletest\c++consoletest\test.cpp(34) : error C2296: '<<' : illegal, left operand has type 'const char [7]'
1>c:\documents and settings\manzoor\my documents\visual studio 2005\projects\c++consoletest\c++consoletest\test.cpp(34) : error C2297: '<<' : illegal, right operand has type 'const char [15]'
1>Build log was saved at "file://c:\Documents and Settings\manzoor\My Documents\Visual Studio 2005\Projects\C++ConsoleTest\C++ConsoleTest\Debug\BuildLog.htm"
1>C++ConsoleTest - 2 error(s), 1 warning(s)
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========

Well, it would be great if told how to resolve the warning

[matsp]

You may want to put parenthesis around your ternary operator.

--
Mats

[manzoor]

#include <iostream>
#include <string>
using namespace std;

int main()
{
	string letters = "Madam I'm Adam";
	size_t length = letters.length();
	bool isPalindrome;
	unsigned index = 0;
	string testStr;
	
	// Lowercase all the characters
	// extract the letters without including punctuation and spaces
	while (index < length)
	{
		if (isalpha(letters[index]))		
			testStr += tolower(letters[index]);

		index++;
	}

	

	// Now check if it is a palindrome
	isPalindrome = true;
	for (int i = 0; i < (testStr.length() / 2); i++)
	{
		if (testStr[i] != testStr[testStr.length() - (i-1)])
		{
			isPalindrome = false;
			break;
		}
	}
	cout << "\"" << letters << "\" " << (isPalindrome ? "is" : "is not")
		 << " a palindrome." << endl;

	return EXIT_SUCCESS;

}

it compiled successfully but the it isn't producing correct results

could you spot the mistake

what I'm entering is "Madam I'm Adam."
which would be evaluated to "madamimadam"

in which case it is a palindrome but the program showing it isnt

IN code::blocks im able to compile it and also in visual studio

but in visual studio when I run i get a string subscript out of range error during the run time? whats the error

[rags_to_riches]

The warning can be resolved by making i in your for loop an unsigned int, as that's what is returned by string.length().

[manzoor]

it compiled successfully but the it isn't producing correct results

could you spot the mistake

what I'm entering is "Madam I'm Adam."
which would be evaluated to "madamimadam"

in which case it is a palindrome but the program showing it isnt

IN code::blocks im able to compile it and also in visual studio

but in visual studio when I run i get a string subscript out of range error during the run time? whats the error

[matsp]

The Visual studio error is a key, isn't it. Why don't you add some output to show you what you are actually comparing?

--
Mats

[anon]

How good is your math?

testStr.length() - (i-1)

[manzoor]

Very bad,


what i wanted was testStr.length() - i - 1;


thanks anon

[robwhit]

umm... that's the same thing.

[laserlight]

umm... that's the same thing.

No, since testStr.length() - (i-1) is equal to testStr.length() - i + 1.

[matsp]

No, since testStr.length() - (i-1) is equal to testStr.length() - i + 1.

And when i is zero, that's length()+1, which is TWO positions beyond the end of the string.

I actually fixed the problem using length() - (i+1), which is the same as the length() - i - 1 expression. I prefer my variant, as it's clearer to subtract i+1 than it is to subtract i and then subtract 1.

--
Mats

[robwhit]

No, since testStr.length() - (i-1) is equal to testStr.length() - i + 1.

Obviously I'm missing something. How are those equal?

[matsp]

Obviously I'm missing something. How are those equal?

If you massage the math:
-(i-1) -> -i + 1.

--
Mats

[tabstop]

Obviously I'm missing something. How are those equal?

Suppose i equals 5, and suppose the first part is 10. So: 10 - (5-1) = 10 - 4 = 6, while 10 - 5 - 1 = 5 - 1 = 4, and 10 - 5 + 1 = 5 + 1 = 6.

[robwhit]

OIC. thanks.