38 lines
1016 B
Go
38 lines
1016 B
Go
// Copyright 2009 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package math
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// Frexp breaks f into a normalized fraction
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// and an integral power of two.
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// It returns frac and exp satisfying f == frac × 2**exp,
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// with the absolute value of frac in the interval [½, 1).
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//
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// Special cases are:
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// Frexp(±0) = ±0, 0
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// Frexp(±Inf) = ±Inf, 0
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// Frexp(NaN) = NaN, 0
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func Frexp(f float64) (frac float64, exp int) {
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return frexp(f)
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}
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func frexp(f float64) (frac float64, exp int) {
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// TODO(rsc): Remove manual inlining of IsNaN, IsInf
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// when compiler does it for us
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// special cases
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switch {
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case f == 0:
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return f, 0 // correctly return -0
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case f < -MaxFloat64 || f > MaxFloat64 || f != f: // IsInf(f, 0) || IsNaN(f):
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return f, 0
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}
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f, exp = normalize(f)
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x := Float64bits(f)
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exp += int((x>>shift)&mask) - bias + 1
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x &^= mask << shift
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x |= (-1 + bias) << shift
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frac = Float64frombits(x)
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return
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}
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