Thread: Find and replace function

first of all thanks for your help adak I went ahead and renamed remove to remove1. Still no go. Also, I went ahead and did the printf of the source last night and it puts it in in the removeString function. However I cannot find anything wrong with that function. It works fine when I hand something to it from main.. Any ideas on maybe how to rewrite that function or why it might not be working?

Code:

for (j = 0; j < i; j++)
    result[j] = source[j];

These lines copy "source" into "result" up to the specified cut-off point.

Code:

while (source[j + remove] != '\0')
{
    result[j] = source[j + remove];
    j++;
}

These lines copy the skipped over section of "source" to the end of "result" - the loop will terminate before the null character is copied.

Code:

while (result[k] != '\0')
{
    source[k] = result[k];
    k++;
}

These lines depend upon the null character existing in the "result" array, but the null character was never actually copied into that array.

You need to add the null character to the "result" array after the first "while()" loop.

Code:

void removeString (char source[], int i, int remove)
// "i" is where to start removing (from findString) and "remove" is # of characters
// to remove
{
    char result[81];
    int j;
    int k = 0;

    for (j = 0; j < i; j++)
        result[j] = source[j];

    while (source[j + remove] != '\0')
    {
        result[j] = source[j + remove];
        j++;
    }
    result[j] = '\0';  // 'j' was already incremented, so it's already in the
                              // correct position to place the null character

    while (result[k] != '\0')
    {
        source[k] = result[k];
        k++;
    }

   source[k] = '\0';
}

Ding ding ding! And the winner is Matticus!!! Thanks for your fresh eyes man. You have solved it! It works perfectly now.

Originally Posted by Matticus

Code:

while (source[j + remove] != '\0')
{
    result[j] = source[j + remove];
    j++;
}

These lines copy the skipped over section of "source" to the end of "result" - the loop will terminate before the null character is copied.

Any idea how I could terminate the loop right when I get to the null character but include the null character? Or do I have to just add it in manually like I am doing now and like you suggested?

There are ways it can be done. But I'm sleepy, so I have to put coding to rest for the night. It would probably be a good idea to leave that exercise to you, anyhow. There is value in figuring these things out.

For the record, I didn't glance at your code and see the solution. I opened up a notepad file and, by hand, tracked each element of each array for the duration of each loop (using a simplified test case) until I saw the problem. The program will do what you tell it to do - if it doesn't do what you want it to do, then that means you didn't tell it the correct thing. But the point is that a program is predictable, so it shouldn't be difficult (with a program like this) to step through each line of code and see what's going on. That is a very valuable skill that should be developed. Anyway, g'night.

Gotcha thanks for your help.

Sorry hadn't had much time yesterday.
Have you already tried your program with other inputs, e.g. change the call to replaceString() in main():

Code:

int main (void)
{
    char str[] = "one time let this work";
    void replaceString (char source[],char s1[], char s2[]);
    
    replaceString(str, "several", "one");

    return 0;
}

Result:

Code:

$ ./test
several time let this work
*** stack smashing detected ***: ./test terminated
...
Aborted (core dumped)

Your logic/algorithm in insertString() is flawed, because it doesn't work when the inserted string is bigger than the removed. In that case you write characters to "source" beyond its array limits.

Bye, Andreas