How do I format decimals in C?

Question

This is my print statement:

printf("%d     %f\n",kPower, raisePower); 

This is my output:

-4     0.000100
-3     0.001000
-2     0.010000
-1     0.100000
0     1.000000
1     10.000000
2     100.000000
3     1000.000000
4     10000.000000

I want it to be printed like this:

UPDATE

So I made my positive values line up:

-4            0.0
-3            0.0
-2            0.0
-1            0.1
0            1.0
1           10.0
2          100.0
3         1000.0
4        10000.0

This is my new code so far:

printf("%d     %10.1f\n",kPower, raisePower);

I don't know, should I make a for loop to print each one (positive results vs negative result) in a different format?

Answer 1

#include <stdio.h>

char *get_number_formatted(double f)
{
    static char buf[128]; // this function is not thread-safe
    int i, j;

    i = snprintf(buf, 128, "%20.10f", f) - 2;

    for (j = i - 8; i > j; --i)
        if (buf[i] != '0')
            break;

    buf[i + 1] = '\0';
    return buf;
}

int main(void)
{
    int i;
    for (i = -4; i < 5; ++i)
        printf("%5d %s\n", i, get_number_formatted(pow(10.0, i)));
   return 0;
}

http://ideone.com/KBiSu0

Output:

   -4         0.0001
   -3         0.001
   -2         0.01
   -1         0.1
    0         1.0
    1        10.0
    2       100.0
    3      1000.0
    4     10000.0

printf() cannot print a variating length of decimal digits, so basically what I did was print the formatted number into a buffer and then cut the exceeding zeros.

Answer 2

Try calculating the powers first using pow() from math.h and then:

You can use %10f to precede the number with blanks in the example total of 10 spaces:

printf ("Preceding with blanks: %10f \n", 10000.01);

Source: cplusplus.com