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