Newbie Question

[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.