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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
}