Format Adjustment in C

Question

Like for example, I want to have this output

Subtotal           20
Discount(10%)    -  2   //negative sign always have 2 spaces out from '2'

I tried to code like this.

dis = subtotal*discount/100; //dis = 20*10/100
printf("Subtotal%13d\n",subtotal);
printf("Discount(%d%s)%4s-%3d\n",discount,"%"," ",dis);

But what if it has no discount, my output will become like this

Number are moved forward to left hand side

Subtotal           20
Discount(0%)    -  0

Also, if my subtotal and discount are very large.

Negative sign and number are sticking together

Subtotal         1000
Discount(50%)    -500

How to code this until my number never move forward to left hand side or right hand side in between the discount (0%-100%) and always make 2 spaces between negative sign and the numbers (dis) ?

Answer 1

You can do it, using:

• the return of printf which tell you how characters have been printed
• the log10 function which can be used to know the number of character in an integer:

The code could looks like:

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

/* get number of character in a number (when printed)*/
int int_print_size(int number)
{
    if (number < 1) 
        return 1;

    else 
        return 1+log10(number);
}


void print(int subtotal, int discount)
{
    char spaces[] = "             ";

    int dis = subtotal*discount/100; //dis = 20*10/100
    int ref, len[2];

    /* take size of first line as reference */
    ref = printf("Subtotal%13d\n",subtotal);
    /* take the size of first part */
    len[0] = printf("Discount(%d%%)",discount);
    /* compute the printed size of `dis` */
    len[1] = int_print_size(dis);

    /* pad with characters from `spaces` array */
    printf("%.*s-  %d\n\n", ref-4-len[0]-len[1], spaces, dis);           

} 

int main(int argc, char *argv[]){       
    /* tests case */
    print(20, 0);
    print(20, 10);
    print(100, 9);
    print(100, 10);
    print(100, 11);
    print(1000, 50);
    print(100000, 99);

    return 0;
}

With result:

Subtotal           20
Discount(0%)     -  0

Subtotal           20
Discount(10%)    -  2

Subtotal          100
Discount(9%)     -  9

Subtotal          100
Discount(10%)   -  10

Subtotal          100
Discount(11%)   -  11

Subtotal         1000
Discount(50%)  -  500

Subtotal       100000
Discount(99%)-  99000