// Copyright 2010 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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// Logb returns the binary exponent of x.
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//
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// Special cases are:
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// Logb(±Inf) = +Inf
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// Logb(0) = -Inf
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// Logb(NaN) = NaN
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func Logb(x float64) float64 {
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// special cases
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switch {
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case x == 0:
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return Inf(-1)
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case IsInf(x, 0):
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return Inf(1)
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case IsNaN(x):
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return x
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}
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return float64(ilogb(x))
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}
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// Ilogb returns the binary exponent of x as an integer.
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//
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// Special cases are:
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// Ilogb(±Inf) = MaxInt32
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// Ilogb(0) = MinInt32
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// Ilogb(NaN) = MaxInt32
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func Ilogb(x float64) int {
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// special cases
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switch {
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case x == 0:
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return MinInt32
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case IsNaN(x):
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return MaxInt32
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case IsInf(x, 0):
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return MaxInt32
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}
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return ilogb(x)
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}
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// logb returns the binary exponent of x. It assumes x is finite and
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// non-zero.
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func ilogb(x float64) int {
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x, exp := normalize(x)
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return int((Float64bits(x)>>shift)&mask) - bias + exp
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}
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