How to produce a NaN float in c?

Question

float f = (float)\'a\';
if(f < 0){ 
}   
else if(f == 0){ 
}   
else if(f > 0){ 
}   
else{
    printf(\"NaN\\n\");                                                     


        

Answer 1

A -nan can also be produced by setting all 32 bits of a float variable as 1, as shown below:

float nan_val = 0xffffffff;

Also, you can compare if a float variable is -nan explicitly by checking if comparison with itself fails.

if (nan_val != nan_val) {
// executes iff nan_val is -nan
}

This method of comparison should work for compilers that use IEEE floats.