IsNan

Reports whether a value is a NaN.

Module: Format

Signature

func IsNan(value: float64) -> bool;
func IsNan(value: float32) -> bool;

Parameters

Name	Type	Description
value	float64 / float32	The value to test.

Returns

true when the value is a NaN — the result of 0.0 / 0.0, of an infinity minus an infinity, and of every arithmetic operation that has no answer at all.

A NaN is the only value that is not equal to itself, which is the whole test: no bit pattern is read, and every NaN answers true regardless of its payload or its sign.

Because every comparison against a NaN is false, a NaN is not infinite and not finite either — IsInfinite and IsFinite both answer false for one, so the three functions partition the values rather than overlapping.

Example

import Format::IsNan;

let nan = 0.0 / 0.0;

IsNan(nan);       // true
IsNan(1.0);       // false
IsNan(1.0 / 0.0); // false -- an infinity is a value, just not a finite one

nan == nan;       // false -- a NaN is the only value not equal to itself

See also

• Format — the module overview
• IsInfinite — whether the value is one of the two infinities
• IsFinite — whether the value is an ordinary number
• ToString — a NaN converts to the text NaN