mirror of https://github.com/golang/go.git
31 lines
697 B
Go
31 lines
697 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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// Ldexp is the inverse of Frexp.
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// It returns frac × 2^exp.
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func Ldexp(frac float64, exp int) float64 {
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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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if frac != frac { // IsNaN(frac)
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return NaN()
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}
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x := Float64bits(frac)
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exp += int(x>>shift) & mask
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if exp <= 0 {
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return 0 // underflow
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}
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if exp >= mask { // overflow
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if frac < 0 {
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return Inf(-1)
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}
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return Inf(1)
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}
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x &^= mask << shift
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x |= uint64(exp) << shift
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return Float64frombits(x)
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}
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