go const 源码

golang const 代码

文件路径：/test/const.go

// run

// 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.

// Test simple boolean and numeric constants.

package main

import "os"

const (
	c0      = 0
	cm1     = -1
	chuge   = 1 << 100
	chuge_1 = chuge - 1
	c1      = chuge >> 100
	c3div2  = 3 / 2
	c1e3    = 1e3

	rsh1 = 1e100 >> 1000
	rsh2 = 1e302 >> 1000

	ctrue  = true
	cfalse = !ctrue

	// Issue #34563
	_ = string(int(123))
	_ = string(rune(456))
)

const (
	f0              = 0.0
	fm1             = -1.
	fhuge   float64 = 1 << 100
	fhuge_1 float64 = chuge - 1
	f1      float64 = chuge >> 100
	f3div2          = 3. / 2.
	f1e3    float64 = 1e3
)

func assert(t bool, s string) {
	if !t {
		panic(s)
	}
}

func ints() {
	assert(c0 == 0, "c0")
	assert(c1 == 1, "c1")
	assert(chuge > chuge_1, "chuge")
	assert(chuge_1+1 == chuge, "chuge 1")
	assert(chuge+cm1+1 == chuge, "cm1")
	assert(c3div2 == 1, "3/2")
	assert(c1e3 == 1000, "c1e3 int")
	assert(c1e3 == 1e3, "c1e3 float")
	assert(rsh1 == 0, "rsh1")
	assert(rsh2 == 9, "rsh2")

	// verify that all (in range) are assignable as ints
	var i int
	i = c0
	assert(i == c0, "i == c0")
	i = cm1
	assert(i == cm1, "i == cm1")
	i = c1
	assert(i == c1, "i == c1")
	i = c3div2
	assert(i == c3div2, "i == c3div2")
	i = c1e3
	assert(i == c1e3, "i == c1e3")

	// verify that all are assignable as floats
	var f float64
	f = c0
	assert(f == c0, "f == c0")
	f = cm1
	assert(f == cm1, "f == cm1")
	f = chuge
	assert(f == chuge, "f == chuge")
	f = chuge_1
	assert(f == chuge_1, "f == chuge_1")
	f = c1
	assert(f == c1, "f == c1")
	f = c3div2
	assert(f == c3div2, "f == c3div2")
	f = c1e3
	assert(f == c1e3, "f == c1e3")
}

func floats() {
	assert(f0 == c0, "f0")
	assert(f1 == c1, "f1")
	// TODO(gri): exp/ssa/interp constant folding is incorrect.
	if os.Getenv("GOSSAINTERP") == "" {
		assert(fhuge == fhuge_1, "fhuge") // float64 can't distinguish fhuge, fhuge_1.
	}
	assert(fhuge_1+1 == fhuge, "fhuge 1")
	assert(fhuge+fm1+1 == fhuge, "fm1")
	assert(f3div2 == 1.5, "3./2.")
	assert(f1e3 == 1000, "f1e3 int")
	assert(f1e3 == 1.e3, "f1e3 float")

	// verify that all (in range) are assignable as ints
	var i int
	i = f0
	assert(i == f0, "i == f0")
	i = fm1
	assert(i == fm1, "i == fm1")

	// verify that all are assignable as floats
	var f float64
	f = f0
	assert(f == f0, "f == f0")
	f = fm1
	assert(f == fm1, "f == fm1")
	f = fhuge
	assert(f == fhuge, "f == fhuge")
	f = fhuge_1
	assert(f == fhuge_1, "f == fhuge_1")
	f = f1
	assert(f == f1, "f == f1")
	f = f3div2
	assert(f == f3div2, "f == f3div2")
	f = f1e3
	assert(f == f1e3, "f == f1e3")
}

func interfaces() {
	var (
		nilN interface{}
		nilI *int
		five = 5

		_ = nil == interface{}(nil)
		_ = interface{}(nil) == nil
	)
	ii := func(i1 interface{}, i2 interface{}) bool { return i1 == i2 }
	ni := func(n interface{}, i int) bool { return n == i }
	in := func(i int, n interface{}) bool { return i == n }
	pi := func(p *int, i interface{}) bool { return p == i }
	ip := func(i interface{}, p *int) bool { return i == p }

	assert((interface{}(nil) == interface{}(nil)) == ii(nilN, nilN),
		"for interface{}==interface{} compiler == runtime")

	assert(((*int)(nil) == interface{}(nil)) == pi(nilI, nilN),
		"for *int==interface{} compiler == runtime")
	assert((interface{}(nil) == (*int)(nil)) == ip(nilN, nilI),
		"for interface{}==*int compiler == runtime")

	assert((&five == interface{}(nil)) == pi(&five, nilN),
		"for interface{}==*int compiler == runtime")
	assert((interface{}(nil) == &five) == ip(nilN, &five),
		"for interface{}==*int compiler == runtime")

	assert((5 == interface{}(5)) == ni(five, five),
		"for int==interface{} compiler == runtime")
	assert((interface{}(5) == 5) == in(five, five),
		"for interface{}==int comipiler == runtime")
}

// Test that typed floating-point and complex arithmetic
// is computed with correct precision.
func truncate() {
	const (
		x30 = 1 << 30
		x60 = 1 << 60

		staticF32 = float32(x30) + 1 - x30
		staticF64 = float64(x60) + 1 - x60
		staticC64 = complex64(x30) + 1 - x30
		staticC128 = complex128(x60) + 1 - x60
	)
	dynamicF32 := float32(x30)
	dynamicF32 += 1
	dynamicF32 -= x30

	dynamicF64 := float64(x60)
	dynamicF64 += 1
	dynamicF64 -= x60

	dynamicC64 := complex64(x30)
	dynamicC64 += 1
	dynamicC64 -= x30

	dynamicC128 := complex128(x60)
	dynamicC128 += 1
	dynamicC128 -= x60

	assert(staticF32 == 0, "staticF32 == 0")
	assert(staticF64 == 0, "staticF64 == 0")
	assert(dynamicF32 == 0, "dynamicF32 == 0")
	assert(dynamicF64 == 0, "dynamicF64 == 0")
	assert(staticC64 == 0, "staticC64 == 0")
	assert(staticC128 == 0, "staticC128 == 0")
	assert(dynamicC64 == 0, "dynamicC64 == 0")
	assert(dynamicC128 == 0, "dynamicC128 == 0")
}

func main() {
	ints()
	floats()
	interfaces()
	truncate()

	assert(ctrue == true, "ctrue == true")
	assert(cfalse == false, "cfalse == false")
}

相关信息

go 源码目录

相关文章

go 235 源码

go 64bit 源码

go alg 源码

go alias 源码

go alias1 源码

go alias2 源码

go alias3 源码

go align 源码

go append 源码

go append1 源码