printing the integral part of a floating point number

Question

I am trying to figure out how to print floating point numbers without using library functions. Printing the decimal part of a floating point number turned out to be quite ea

Answer 1

/Edit: Read Unni's answer first. This results come from http://codepad.org/TLqQzLO3.

void print_integral_part(float value)
{
    printf("input : %f\n", value);
    char a[129]; // worst case is 128 digits for base 2 plus NUL
    char * p = a + 128;
    *p = 0;
    do
    {
        int digit = fmod(value, base);
        value /= base;
        printf("interm: %f\n", value);
        *--p = hex[digit];
    } while (value >= 1);
    printf("result: %s\n", p);
}

print_integral_part(3.40282347e+38F);

to see how messed up your value gets by the value /= base operation:

input : 340282346638528859811704183484516925440.000000
interm: 34028234663852885981170418348451692544.000000
interm: 3402823466385288480057879763104038912.000000
interm: 340282359315034876851393457419190272.000000
interm: 34028234346940236846450271659753472.000000
interm: 3402823335658820218996583884128256.000000
interm: 340282327376181848531187106054144.000000
interm: 34028232737618183051678859657216.000000
interm: 3402823225404785588136713388032.000000
interm: 340282334629736780292710989824.000000
interm: 34028231951816403862828351488.000000
interm: 3402823242405304929106264064.000000
interm: 340282336046446683592065024.000000
interm: 34028232866774907300610048.000000
interm: 3402823378911210969759744.000000
interm: 340282332126513595416576.000000
interm: 34028233212651357863936.000000
interm: 3402823276229139890176.000000
interm: 340282333252413489152.000000
interm: 34028234732616232960.000000
interm: 3402823561222553600.000000
interm: 340282356122255360.000000
interm: 34028235612225536.000000
interm: 3402823561222553.500000
interm: 340282366859673.625000
interm: 34028237357056.000000
interm: 3402823735705.600098
interm: 340282363084.799988
interm: 34028237619.200001
interm: 3402823680.000000
interm: 340282368.000000
interm: 34028236.800000
interm: 3402823.600000
interm: 340282.350000
interm: 34028.234375
interm: 3402.823438
interm: 340.282349
interm: 34.028235
interm: 3.402824
interm: 0.340282
result: 340282368002860660002286082464244022240

When in doubt, throw more printfs at it ;)