golang floor 代码
文件路径：/src/math/floor.go
/ 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
/ Floor returns the greatest integer value less than or equal to x.
/
/ Special cases are:
/
/ Floor(±0) = ±0
/ Floor(±Inf) = ±Inf
/ Floor(NaN) = NaN
func Floor(x float64) float64 {
if haveArchFloor {
return archFloor(x)
}
return floor(x)
}
func floor(x float64) float64 {
if x == 0 || IsNaN(x) || IsInf(x, 0) {
return x
}
if x < 0 {
d, fract := Modf(-x)
if fract != 0.0 {
d = d + 1
}
return -d
}
d, _ := Modf(x)
return d
}
/ Ceil returns the least integer value greater than or equal to x.
/
/ Special cases are:
/
/ Ceil(±0) = ±0
/ Ceil(±Inf) = ±Inf
/ Ceil(NaN) = NaN
func Ceil(x float64) float64 {
if haveArchCeil {
return archCeil(x)
}
return ceil(x)
}
func ceil(x float64) float64 {
return -Floor(-x)
}
/ Trunc returns the integer value of x.
/
/ Special cases are:
/
/ Trunc(±0) = ±0
/ Trunc(±Inf) = ±Inf
/ Trunc(NaN) = NaN
func Trunc(x float64) float64 {
if haveArchTrunc {
return archTrunc(x)
}
return trunc(x)
}
func trunc(x float64) float64 {
if x == 0 || IsNaN(x) || IsInf(x, 0) {
return x
}
d, _ := Modf(x)
return d
}
/ Round returns the nearest integer, rounding half away from zero.
/
/ Special cases are:
/
/ Round(±0) = ±0
/ Round(±Inf) = ±Inf
/ Round(NaN) = NaN
func Round(x float64) float64 {
/ Round is a faster implementation of:
/
/ func Round(x float64) float64 {
/ t := Trunc(x)
/ if Abs(x-t) >= 0.5 {
/ return t + Copysign(1, x)
/ }
/ return t
/ }
bits := Float64bits(x)
e := uint(bits>>shift) & mask
if e < bias {
/ Round abs(x) < 1 including denormals.
bits &= signMask / +-0
if e == bias-1 {
bits |= uvone / +-1
}
} else if e < bias+shift {
/ Round any abs(x) >= 1 containing a fractional component [0,1).
/
/ Numbers with larger exponents are returned unchanged since they
/ must be either an integer, infinity, or NaN.
const half = 1 << (shift - 1)
e -= bias
bits += half >> e
bits &^= fracMask >> e
}
return Float64frombits(bits)
}
/ RoundToEven returns the nearest integer, rounding ties to even.
/
/ Special cases are:
/
/ RoundToEven(±0) = ±0
/ RoundToEven(±Inf) = ±Inf
/ RoundToEven(NaN) = NaN
func RoundToEven(x float64) float64 {
/ RoundToEven is a faster implementation of:
/
/ func RoundToEven(x float64) float64 {
/ t := math.Trunc(x)
/ odd := math.Remainder(t, 2) != 0
/ if d := math.Abs(x - t); d > 0.5 || (d == 0.5 && odd) {
/ return t + math.Copysign(1, x)
/ }
/ return t
/ }
bits := Float64bits(x)
e := uint(bits>>shift) & mask
if e >= bias {
/ Round abs(x) >= 1.
/ - Large numbers without fractional components, infinity, and NaN are unchanged.
/ - Add 0.499.. or 0.5 before truncating depending on whether the truncated
/ number is even or odd (respectively).
const halfMinusULP = (1 << (shift - 1)) - 1
e -= bias
bits += (halfMinusULP + (bits>>(shift-e))&1) >> e
bits &^= fracMask >> e
} else if e == bias-1 && bits&fracMask != 0 {
/ Round 0.5 < abs(x) < 1.
bits = bits&signMask | uvone / +-1
} else {
/ Round abs(x) <= 0.5 including denormals.
bits &= signMask / +-0
}
return Float64frombits(bits)
}