3 replies to this topic

[british0zzy]

I'm writing a program that removes tabs from the input and replaces it with the correct number of spaces. It's giving me odd results, which I can't quite figure out why. If you could look at this short program and give me some pointers, it'd be greatly appreciated :)

#include <stdio.h>


#define TABLENGTH 4


main()

{

    int n; /* Position of cursor relative to tab stops */

    int c;

    

    n = TABLENGTH;  /* Setting n to TABLENGTH is functionally equivalent to setting it to zero, but will make calculations easier */

    while ((c=getchar()) != EOF) {

        if (n > TABLENGTH)

            n = 1;  /* Should this be n = n - TABLENGTH? */

        if (c != '\t') {

            putchar(c);

            if (c == '\n')

                n = TABLENGTH; /* A newline resets the cursor to 'zero' */

            else

                ++n;

        }

        else {

            for (c = 0; c < n; ++c)

                putchar(' ');

            n = TABLENGTH;  /* Tabs reset cursor to 'zero' */

        }

    }

    return 0;

}

[dargueta]

You're making this too complicated. Try this.

#include <stdio.h>


#define    TABLEN    4


void main(void)

{

    int ch, i;

    while((ch = getchar()) != EOF)

    {

        if(ch == '\t')

        {

            for(i = 0; i < TABLEN; ++i)

                putchar(' ');

        }

        else

            putchar(ch);

    }

}

[british0zzy]

ok, I didn't explain the objective of the program clearly. I am assuming there are fixed tab stops every n columns. So if I the input is "12'\t'34", the output should be "12**34". Or if I typed "12345'\t'6", the output should be "12345***6". (The *'s are spaces and '\t' is obviously a tab.)
Does that make more sense?
My earlier version works perfectly except when you skip to a new line, it breaks because skipping to a newline resets the cursor to the beginning.
Here's the earlier code:

#include <stdio.h>

#define TABLENGTH   4

main()
{
    int n; /* Position of cursor relative to tab stops */
    int c;
    
    n = TABLENGTH;  /* Setting n to TABLENGTH is functionally equivalent to setting it to zero, but will make calculations easier */
    while ((c=getchar()) != EOF) {
        if (n > TABLENGTH)
            n = 1;  /* Should this be n = n - TABLENGTH? */
        if (c != '\t') {
            putchar(c);
            ++n;
        }
        else {
            for (c = 0; c < n; ++c)
                putchar(' ');
            n = TABLENGTH;  /* Tabs reset cursor to 'zero' */
        }
    }
    return 0;
}

[dargueta]

OOOH. I see now...so I'm assuming you get n somewhere beforehand, along with some input to parse, right? If you don't want to have it reset at a newline, just add another if statement.