c++ - strange output in comparison of float with float literal

Question

float f = 0.7;
if( f == 0.7 )
    printf("equal");
else
    printf("not equal");

Why is the output not equal ?

Why does this happen?

question from:https://stackoverflow.com/questions/1839422/strange-output-in-comparison-of-float-with-float-literal

Answer 1

This happens because in your statement

  if(f == 0.7)

the 0.7 is treated as a double. Try 0.7f to ensure the value is treated as a float:

  if(f == 0.7f)

But as Michael suggested in the comments below you should never test for exact equality of floating-point values.