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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

const (

        uvnan    = 0x7FF0000000000001

        uvinf    = 0x7FF0000000000000

        uvneginf = 0xFFF0000000000000

        mask     = 0x7FF

        shift    = 64 - 11 - 1

        bias     = 1023

)

// Inf returns positive infinity if sign >= 0, negative infinity if sign < 0.

func Inf(sign int) float64 {

        var v uint64

        if sign >= 0 {

                v = uvinf

        } else {

                v = uvneginf

        }

        return Float64frombits(v)

}

// NaN returns an IEEE 754 ``not-a-number'' value.

func NaN() float64 { return Float64frombits(uvnan) }

// IsNaN returns whether f is an IEEE 754 ``not-a-number'' value.

func IsNaN(f float64) (is bool) {

        // IEEE 754 says that only NaNs satisfy f != f.

        // To avoid the floating-point hardware, could use:

        //      x := Float64bits(f);

        //      return uint32(x>>shift)&mask == mask && x != uvinf && x != uvneginf

        return f != f

}

// IsInf returns whether f is an infinity, according to sign.

// If sign > 0, IsInf returns whether f is positive infinity.

// If sign < 0, IsInf returns whether f is negative infinity.

// If sign == 0, IsInf returns whether f is either infinity.

func IsInf(f float64, sign int) bool {

        // Test for infinity by comparing against maximum float.

        // To avoid the floating-point hardware, could use:

        //      x := Float64bits(f);

        //      return sign >= 0 && x == uvinf || sign <= 0 && x == uvneginf;

        return sign >= 0 && f > MaxFloat64 || sign <= 0 && f < -MaxFloat64

}

// normalize returns a normal number y and exponent exp

// satisfying x == y × 2**exp. It assumes x is finite and non-zero.

func normalize(x float64) (y float64, exp int) {

        const SmallestNormal = 2.2250738585072014e-308 // 2**-1022

        if Abs(x) < SmallestNormal {

                return x * (1 << 52), -52

        }

        return x, 0

}