mirror of git://gcc.gnu.org/git/gcc.git
144 lines
3.6 KiB
Go
144 lines
3.6 KiB
Go
// Copyright 2015 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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// +build ignore
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package big_test
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import (
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"fmt"
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"math"
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"math/big"
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)
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func ExampleFloat_Add() {
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// Operating on numbers of different precision.
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var x, y, z big.Float
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x.SetInt64(1000) // x is automatically set to 64bit precision
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y.SetFloat64(2.718281828) // y is automatically set to 53bit precision
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z.SetPrec(32)
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z.Add(&x, &y)
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fmt.Printf("x = %.10g (%s, prec = %d, acc = %s)\n", &x, x.Text('p', 0), x.Prec(), x.Acc())
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fmt.Printf("y = %.10g (%s, prec = %d, acc = %s)\n", &y, y.Text('p', 0), y.Prec(), y.Acc())
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fmt.Printf("z = %.10g (%s, prec = %d, acc = %s)\n", &z, z.Text('p', 0), z.Prec(), z.Acc())
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// Output:
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// x = 1000 (0x.fap+10, prec = 64, acc = Exact)
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// y = 2.718281828 (0x.adf85458248cd8p+2, prec = 53, acc = Exact)
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// z = 1002.718282 (0x.faadf854p+10, prec = 32, acc = Below)
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}
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func Example_Shift() {
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// Implementing Float "shift" by modifying the (binary) exponents directly.
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for s := -5; s <= 5; s++ {
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x := big.NewFloat(0.5)
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x.SetMantExp(x, x.MantExp(nil)+s) // shift x by s
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fmt.Println(x)
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}
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// Output:
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// 0.015625
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// 0.03125
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// 0.0625
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// 0.125
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// 0.25
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// 0.5
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// 1
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// 2
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// 4
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// 8
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// 16
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}
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func ExampleFloat_Cmp() {
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inf := math.Inf(1)
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zero := 0.0
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operands := []float64{-inf, -1.2, -zero, 0, +1.2, +inf}
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fmt.Println(" x y cmp")
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fmt.Println("---------------")
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for _, x64 := range operands {
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x := big.NewFloat(x64)
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for _, y64 := range operands {
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y := big.NewFloat(y64)
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fmt.Printf("%4g %4g %3d\n", x, y, x.Cmp(y))
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}
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fmt.Println()
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}
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// Output:
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// x y cmp
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// ---------------
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// -Inf -Inf 0
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// -Inf -1.2 -1
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// -Inf -0 -1
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// -Inf 0 -1
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// -Inf 1.2 -1
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// -Inf +Inf -1
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//
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// -1.2 -Inf 1
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// -1.2 -1.2 0
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// -1.2 -0 -1
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// -1.2 0 -1
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// -1.2 1.2 -1
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// -1.2 +Inf -1
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//
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// -0 -Inf 1
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// -0 -1.2 1
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// -0 -0 0
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// -0 0 0
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// -0 1.2 -1
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// -0 +Inf -1
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//
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// 0 -Inf 1
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// 0 -1.2 1
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// 0 -0 0
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// 0 0 0
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// 0 1.2 -1
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// 0 +Inf -1
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//
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// 1.2 -Inf 1
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// 1.2 -1.2 1
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// 1.2 -0 1
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// 1.2 0 1
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// 1.2 1.2 0
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// 1.2 +Inf -1
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//
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// +Inf -Inf 1
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// +Inf -1.2 1
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// +Inf -0 1
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// +Inf 0 1
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// +Inf 1.2 1
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// +Inf +Inf 0
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}
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func ExampleRoundingMode() {
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operands := []float64{2.6, 2.5, 2.1, -2.1, -2.5, -2.6}
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fmt.Print(" x")
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for mode := big.ToNearestEven; mode <= big.ToPositiveInf; mode++ {
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fmt.Printf(" %s", mode)
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}
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fmt.Println()
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for _, f64 := range operands {
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fmt.Printf("%4g", f64)
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for mode := big.ToNearestEven; mode <= big.ToPositiveInf; mode++ {
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// sample operands above require 2 bits to represent mantissa
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// set binary precision to 2 to round them to integer values
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f := new(big.Float).SetPrec(2).SetMode(mode).SetFloat64(f64)
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fmt.Printf(" %*g", len(mode.String()), f)
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}
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fmt.Println()
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}
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// Output:
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// x ToNearestEven ToNearestAway ToZero AwayFromZero ToNegativeInf ToPositiveInf
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// 2.6 3 3 2 3 2 3
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// 2.5 2 3 2 3 2 3
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// 2.1 2 2 2 3 2 3
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// -2.1 -2 -2 -2 -3 -3 -2
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// -2.5 -2 -3 -2 -3 -3 -2
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// -2.6 -3 -3 -2 -3 -3 -2
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}
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