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Diffstat (limited to 'src/pkg/math/frexp.go')
-rw-r--r-- | src/pkg/math/frexp.go | 28 |
1 files changed, 28 insertions, 0 deletions
diff --git a/src/pkg/math/frexp.go b/src/pkg/math/frexp.go new file mode 100644 index 000000000..8b6d45606 --- /dev/null +++ b/src/pkg/math/frexp.go @@ -0,0 +1,28 @@ +// Copyright 2009 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +package math + +// Frexp breaks f into a normalized fraction +// and an integral power of two. +// It returns frac and exp satisfying f == frac × 2<sup>exp</sup>, +// with the absolute value of frac in the interval [½, 1). +func Frexp(f float64) (frac float64, exp int) { + // TODO(rsc): Remove manual inlining of IsNaN, IsInf + // when compiler does it for us + // special cases + switch { + case f == 0: + return + case f < -MaxFloat64 || f > MaxFloat64 || f != f: // IsInf(f, 0) || IsNaN(f): + frac = f + return + } + x := Float64bits(f) + exp = int((x>>shift)&mask) - bias + x &^= mask << shift + x |= bias << shift + frac = Float64frombits(x) + return +} |