c++cfloating-pointprecision

Strange output in comparison of float with float literal

Consider:

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

Why is the output not equal?

Why does this happen?

Solution

  • 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.