== package:ieee754

(===) :: AEq a => a -> a -> Bool
ieee754 Data.AEq
An exact equality comparison. For real IEEE types, two values are equivalent in the following cases:
  • both values are +0;
  • both values are -0;
  • both values are nonzero and equal to each other (according to ==);
  • both values are NaN with the same payload and sign.
For complex IEEE types, two values are equivalent if their real and imaginary parts are equivalent.
(~==) :: AEq a => a -> a -> Bool
ieee754 Data.AEq
An approximate equality comparison operator. For real IEEE types, two values are approximately equal in the following cases:
  • at least half of their significand bits agree;
  • both values are less than epsilon;
  • both values are NaN.
For complex IEEE types, two values are approximately equal in the followiing cases:
  • their magnitudes are approximately equal and the angle between them is less than 32*epsilon;
  • both magnitudes are less than epsilon;
  • both have a NaN real or imaginary part.
Admitedly, the 32 is a bit of a hack. Future versions of the library may switch to a more principled test of the angle.