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authorupstream source tree <ports@midipix.org>2015-03-15 20:14:05 -0400
committerupstream source tree <ports@midipix.org>2015-03-15 20:14:05 -0400
commit554fd8c5195424bdbcabf5de30fdc183aba391bd (patch)
tree976dc5ab7fddf506dadce60ae936f43f58787092 /libgo/go/math/frexp.go
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diff --git a/libgo/go/math/frexp.go b/libgo/go/math/frexp.go
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+// 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**exp,
+// with the absolute value of frac in the interval [½, 1).
+//
+// Special cases are:
+// Frexp(±0) = ±0, 0
+// Frexp(±Inf) = ±Inf, 0
+// Frexp(NaN) = NaN, 0
+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 f, 0 // correctly return -0
+ case f < -MaxFloat64 || f > MaxFloat64 || f != f: // IsInf(f, 0) || IsNaN(f):
+ return f, 0
+ }
+ f, exp = normalize(f)
+ x := Float64bits(f)
+ exp += int((x>>shift)&mask) - bias + 1
+ x &^= mask << shift
+ x |= (-1 + bias) << shift
+ frac = Float64frombits(x)
+ return
+}