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master
tpl/math/round.go
62 строки
1 KB
Oleksandr Redko
all: Format files with gofmt
05 окт 2023, 15:45
05 окт 2023, 15:45
274852b
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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. // According to https://github.com/golang/go/issues/20100, the Go stdlib will // include math.Round beginning with Go 1.10. // // The following implementation was taken from https://golang.org/cl/43652. package math import "math" const ( mask = 0x7FF shift = 64 - 11 - 1 bias = 1023 ) // 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 // } const ( signMask = 1 << 63 fracMask = 1<<shift - 1 half = 1 << (shift - 1) one = bias << shift ) bits := math.Float64bits(x) e := uint(bits>>shift) & mask if e < bias { // Round abs(x) < 1 including denormals. bits &= signMask // +-0 if e == bias-1 { bits |= one // +-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. e -= bias bits += half >> e bits &^= fracMask >> e } return math.Float64frombits(bits) }