getting no output (expecting boolean output)

Question

So I tried not using the string.h file. I created string length function which works. I then created a function to check if two functions are same or not but I am getting no output. I have tested the string length function and that works. I am not sure what I am doing wrong in the second function. Please point out the error.

#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>

char stringLength(char userString[])
{
    int i=0,count=0;
    while (userString[i] != '\0')
    {
        count = (count + 1);
        i = (i + 1);
    }
    return count;

}


bool stringCheck (char a[], char b[])
{
    bool isEquals = false;
    if (stringLength(a) == stringLength(b))
    {
        int i=0, count=0;
        while (i<stringLength(a))
        {
            if (a[i] == b[i])
            {
                count+=1;
            }

            i+=1;
        }

        if (count == stringLength(a))
            isEquals = true;
        else
            isEquals = false;
    }
    else
        isEquals = false;

    return isEquals;
}

int main()
{
    stringCheck("abcd", "abcd");
    return 0;
}

Answer 1

The function works.

Its just that you are not catching the return value of stringCheck() function. You can do that as shown below.

bool strMatch = stringCheck("abcd", "abcd");
if(true == strMatch)
{
    // Do something when the strings are same
}
else
{
    // Do something else otherwise
}

Also, as an improvement - In stringCheck() function, you have a loop

while (i < stringLength(a))

There is nothing wrong with it, but you can improve the efficiency of your code by saving the length of the string into a variable and use that variable for polling in the while loop. In stringCheck function:

int i=0, count=0;
char strLength = stringLength(a);
while (i < strLength)

This will work because the length of strings aren't changing within the loop.

I find issues with stringLength() function. First is, the data type used for variable returning the length count is int whereas the return type set for function is char. Also, consider changing the return type of the function stringLength() to size_t along with the data type for variable count in the same function.

char stringLength(char userString[])

to

size_t stringLength(char userString[])

With a return type as char, your function will misbehave if the length of the string is more than 127 bytes.

The next improvement in the stringLength() function is, i and count seems to be updated at the same time. I can't think why you need two variables there when you can simply return i in place of count.

Your compiler would have warned you about all these points if you had compiled your code with certain gcc flags such as -Wall to start with.

Answer 2

AS @WedaPashi says, your code works. You just need to use the result.

But your code is overly complicated. There's absolutely no reason whatsoever to use two variables in the first function. Also, the first function should not return a char (unless you want the function to not work on strings longer than 127 or 255 characters) Use int or preferably size_t instead. Do like this:

size_t stringLength(char userString[])
{
    int count=0;
    while (userString[i] != '\0') 
        count++;

    return count;
}

And for your second function, it's just a waste of time comparing their lengths. Here is a much simpler implementation:

bool stringCheck (char a[], char b[])
{
    size_t index = 0;
    while(a[index] != '\0') {
        if(a[index] != b[index]) return false;
        index++;
    }

    return true;
}

If you want you could also add some checking if the arguments are null pointers.

Answer 3

You are not using the return value from the function stringCheck in main

int main()
{
    stringCheck("abcd", "abcd");
    return 0;
}

At least you could write for example

int main( void )
{
    printf( "Strings are %sequal\n", stringCheck("abcd", "abcd") ? "" : "not " );
    return 0;
}

Apart from this your code is very inefficient and in general even can invoke undefined behavior.

For example the function stringLength will return incorrect length of strings that have more than 127 or 255 characters depending on whether the type char behaves as the type signed char or unsigned char.

The function should be declared like

size_t stringLength( const char userString[] )
{
    size_t count = 0;

    while ( userString[count] != '\0' ) ++count;

    return count;
}

Or for example within the function stringCheck the function stringLength is called for each value of the variable i in the loop

    int i=0, count=0;
    while (i<stringLength(a))
             ^^^^^^^^^^^^

The function parameters should be declared with the qualifier const because passed strings are not changed within the function.

In fact the function stringLength is redundant. The function stringCheck can be written without using the function stringLength much simpler.

Here you are.

bool stringCheck( const char *s1, const char *s2 )
{
    while ( *s1 && *s1 == *s2 )
    {
        ++s1;
        ++s2;
    }

    return *s1 == *s2;
}