Thread: How do you create a function that removes certain areas from a string?

Hey guys, I'll get back at you tomorrow if I still need help. Going to try to do it by myself a little longer.

I know if I were to do this, I'd start with a pencil and paper (in this case, graph paper would be a better choice for me personally). Seeing the letters in a grid would help visualize the process, from which an algorithm could be developed.

If there's no restrictions in the homework, you could do this using memmove().

Originally Posted by KCfromNC

If there's no restrictions in the homework, you could do this using memmove().

Well when he asks for a function, he wants us to make our own functions.
This is what I've done so far but I'll get back to you guys later

Code:

int removeString(int argc, char const argv[])
{
    char word[200];
    int i;
    long int len = strlen(word);
    int rem = 13;
    int out = 15;
    /* remove rem'th char from word */
    for (i = rem; i < len - 1; i++) word[i] = word[i + out];
    if(i < len) word[i] = '\0';
    return 0;
}


int main ()
{
    char word[] = "The lunatic, the lover, and the poet, are of imagination all compact.";
    
    printf("%s\n", word);
    removeString(15,13); //incompatible integer to pointer conversion error 
    return 0;
}

Im still working on it.

If i move my function into the main it works though :/

Code:

int main (){
    char word[] = "The lunatic, the lover, and the poet, are of imagination all compact.";
    
    int i;
    long int len = strlen(word);
    int rem = 13;
    int out = 15;
    /* remove rem'th char from word */
    for (i = rem; i < len - 1; i++) word[i] = word[i + out];
    if(i < len) word[i] = '\0';
    
    printf("%s\n", word);
    return 0;
}

It prints "The lunatic, the poet, are of imagination all compact."

In post #6, you're trying to access elements way outside the bounds of your array. I added a line for you:

Code:

#include <stdio.h>
#include <string.h>

int main(void)
{
    char word[] = "The lunatic, the lover, and the poet, are of imagination all compact.";
    int i;
    int len = strlen(word);
    int rem = 13;
    int out = 15;

    /* remove rem'th char from word */
    for (i = rem; i < len - 1; i++)
    {
        word[i] = word[i + out];
        printf("word[i + out] is accessing element %2d out of %d\n",i+out,sizeof(word)); /* added */
    }
    if(i < len) word[i] = '\0';

    printf("%s\n", word);
    return 0;
}

In post #5:

- You're not passing the expected values to your function (it expect an int and a char array) - hence the warning
- You don't use the char array you pass, but instead use another char array ("word") that is not initialized

It prints what I wanted.

Code:

int returnString(char word[], int x, int y)
{
    int i;
    long int len = strlen(word);
    int rem = x;
    int out = y;
    /* remove rem'th char from word */
    for (i = rem; i < len - 1; i++) word[i] = word[i + out];
    if(i < len) word[i] = '\0';
    return 0;
}


int main ()
{
    char text[] = "The lunatic, the lover, and the poet, are of imagination all compact.";
    returnString(text, 13, 15);
    printf("%s\n", text);
    return 0;
}

Not sure why you posted it, but the one big thing I noticed:

Code:

int returnString(char word[], int x, int y)
{
...
    int rem = x;
    int out = y;

What's wrong with ditching the local variables and naming your parameters rem and out?

Code:

int returnString(char word[], int rem, int out)

Or better yet, name your function removeString, per the directions, and pick even more descriptive names for the parameters (it can accept a string with multiple words, or no words at all; rem might be remove, but what is out?). And it doesn't need to return anything, so make it void:

Code:

void removeString(char text[], int start_index, int remove_length)

Other than that, does it work? Did you test it? Did you test it in ways that can break it? Like start_index is greater than the length of the text? What about ways to break it with different values of remove_length? What happens if start_index or remove_length are negative? Perhaps unsigned int would be better.

While I couldn't get this homework to work yesterday, I was working on this one.

Code:

void insertString(char string[], char c[], int idx)
{
    //long int len = strlen(string);
    char stringtwo[2000] = "";
    int i;
    i = 0;
    while ((string[i] = c[i]) != '\0') {
        i++;
        strcpy(stringtwo,string);
        strcpy(stringtwo,c);
    }
    printf("%s", stringtwo);
}


int main()
{
    char text[ 200 ] = "Doubt I love.";
    insertString(text, "thou the stars are fire;\n Doubt that ", 5);
    insertString(text, "the sun doth move;\n Doubt ", 42);
    insertString(text, "truth to be a liar;\n But never doubt ", 68);
    printf(" %s\n", text );
}

This is what it prints

Code:

thou the stars are fire;
 Doubt that the sun doth move;
 Doubt truth to be a liar;
 But never doubt  truth to be a liar;
 But never doubt

This is what it's supposed to print.

Code:

{Doubt }thou the stars are fire;
Doubt that the sun doth move;
Doubt truth to be a liar;
But never doubt {I love.}

Originally Posted by Cdd101

It prints what I wanted.

This time, perhaps. But that's what happens with undefined behavior - it can seem to work as you want it, or anything else can happen. Who's to say it will work right when your professor tries running it on their setup?

J.2 Undefined behavior
The behavior is undefined in the following circumstances:

...

An array subscript is out of range, even if an object is apparently accessible with the
given subscript (as in the lvalue expression a[1][7] given the declaration int
a[4][5]) (6.5.6).

Well it seems in my homework_2 i had such an idiotic mistake

I'm able to at least make it a little better now.

Code:

void insertString(char text[], char c[], int idx) {
    char stringtwo[2000] = "";
    int i;
    i = 0;
    while ((text[i] = c[i]) != '\0') {
        i++;
        strcpy(stringtwo,text);
        strcpy(stringtwo,c);
    }
    printf("%s", stringtwo);
}


int main()
{
    char text[ 200 ] = "Doubt I love.";
    insertString(text, "thou the stars are fire;\n Doubt that ", 5);
    insertString(text, "the sun doth move;\n Doubt ", 42);
    insertString(text, "truth to be a liar;\n But never doubt ", 68);
    printf(" %s\n", text );
 
}

Not the desired out put I want though yet.

Code:

thou the stars are fire;
 Doubt that the sun doth move;
 Doubt truth to be a liar;
 But never doubt  truth to be a liar;
 But never doubt

Originally Posted by Cdd101

My bad about using meaningless variable names.

Is this what you're asking me to do?

Yep, that's what I was suggesting. Makes your code much easier to read and understand, which means you're less likely to make mistakes.

Originally Posted by Cdd101

It works.

Well, you've proven it works for that one test case, is that really sufficient? What if you change start_index to 60? What if remove_length is longer than the actual string? What about passing in negative values? Does it still work? Is it possible somebody might call your funciton with invalid parameters (e.g. your teacher when testing)? Should you be doing any more error checking? The assignment doesn't say one way or the other, so I would err on the side of caution. Maybe email your prof to be sure.