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Function std.math.operations.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);


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


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);


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


Boost License 1.0.