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Function `std.math.feqrel`

To what precision is x equal to y?


						
				int feqrel(X)
				(
				

				  const X x,
				

				  const X y
				

				) pure nothrow @nogc @trusted
				

				if (isFloatingPoint!X);

Returns

the number of mantissa bits which are equal in x and y. eg, 0x1.F8p+60 and 0x1.F1p+60 are equal to 5 bits of precision.

Special Values
x	y	feqrel(x, y)
x	x	real.mant_dig
x	>= 2*x	0
x	<= x/2	0
NAN	any	0
any	NAN	0

Example

writeln(feqrel(2.0, 2.0)); // 53
writeln(feqrel(2.0f, 2.0f)); // 24
writeln(feqrel(2.0, double.nan)); // 0

// Test that numbers are within n digits of each
// other by testing if feqrel > n * log2(10)

// five digits
assert(feqrel(2.0, 2.00001) > 16);
// ten digits
assert(feqrel(2.0, 2.00000000001) > 33);

Authors

Walter Bright, Don Clugston, Conversion of CEPHES math library to D by Iain Buclaw and David Nadlinger

License

Boost License 1.0.