float.c

// we link against asm lib floatlib.s (this repo) which does things like float addition
// x87 functions like FLD are confined to this library
// Cannot write out floats with printf as it is a vararg and takes doubles (not supported)
// instead we write out as hex integers and check value using
// https://www.h-schmidt.net/FloatConverter/IEEE754.html

//#include <stdio.h>
//#include <math.h>

float sinf(float); // external, from math.h (c99 or later)

float pi=3.1415;

float square(float x)
{
    return x*x;
}

int main()
{
    float a;
    int i=1;
    a=5.0;

    printf("numbers: %0x %0x\n", pi, a);

    a+=2;   // promote 2 to 2.0. a=7.0
    
    printf("result: %0x %0x %0x\n", a+3.5, a+pi, a-1.5); // 10.5 (41280000), 10.1415 (41224396), 5.5 (40b00000)
    
    float b=-3.0;
    printf("b=%0x, i=%d, i(converted)=%0x, sq=%0x\n", b, i, (float)i, square(b));  // -3.0 (c0400000) 1 3f800000 sq=41100000
    
    // a=7.0, b=-3.0
    
    if (a>b)
        printf("a>b\n");

    if (a>=b)
        printf("a>=b\n");

    if (a<b)
        printf("a<b\n");

    if (a<=b)
        printf("a<=b\n");

    if (b>a)
        printf("b>a\n");

    if (b>=a)
        printf("b>=a\n");

    if (b<a)
        printf("b<a\n");

    if (b<=a)
        printf("b<=a, sinf(a)=%0x\n", sinf(a));
    
    i=3+a; // promote to 3.0, add to get 10.0, demote to 10
    return i+1; // 11
}