1// Copyright 2015 The Go Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style
3// license that can be found in the LICENSE file.
4
5package big_test
6
7import (
8	"fmt"
9	"math"
10	"math/big"
11)
12
13func ExampleFloat_Add() {
14	// Operate on numbers of different precision.
15	var x, y, z big.Float
16	x.SetInt64(1000)          // x is automatically set to 64bit precision
17	y.SetFloat64(2.718281828) // y is automatically set to 53bit precision
18	z.SetPrec(32)
19	z.Add(&x, &y)
20	fmt.Printf("x = %.10g (%s, prec = %d, acc = %s)\n", &x, x.Text('p', 0), x.Prec(), x.Acc())
21	fmt.Printf("y = %.10g (%s, prec = %d, acc = %s)\n", &y, y.Text('p', 0), y.Prec(), y.Acc())
22	fmt.Printf("z = %.10g (%s, prec = %d, acc = %s)\n", &z, z.Text('p', 0), z.Prec(), z.Acc())
23	// Output:
24	// x = 1000 (0x.fap+10, prec = 64, acc = Exact)
25	// y = 2.718281828 (0x.adf85458248cd8p+2, prec = 53, acc = Exact)
26	// z = 1002.718282 (0x.faadf854p+10, prec = 32, acc = Below)
27}
28
29func ExampleFloat_shift() {
30	// Implement Float "shift" by modifying the (binary) exponents directly.
31	for s := -5; s <= 5; s++ {
32		x := big.NewFloat(0.5)
33		x.SetMantExp(x, x.MantExp(nil)+s) // shift x by s
34		fmt.Println(x)
35	}
36	// Output:
37	// 0.015625
38	// 0.03125
39	// 0.0625
40	// 0.125
41	// 0.25
42	// 0.5
43	// 1
44	// 2
45	// 4
46	// 8
47	// 16
48}
49
50func ExampleFloat_Cmp() {
51	inf := math.Inf(1)
52	zero := 0.0
53
54	operands := []float64{-inf, -1.2, -zero, 0, +1.2, +inf}
55
56	fmt.Println("   x     y  cmp")
57	fmt.Println("---------------")
58	for _, x64 := range operands {
59		x := big.NewFloat(x64)
60		for _, y64 := range operands {
61			y := big.NewFloat(y64)
62			fmt.Printf("%4g  %4g  %3d\n", x, y, x.Cmp(y))
63		}
64		fmt.Println()
65	}
66
67	// Output:
68	//    x     y  cmp
69	// ---------------
70	// -Inf  -Inf    0
71	// -Inf  -1.2   -1
72	// -Inf    -0   -1
73	// -Inf     0   -1
74	// -Inf   1.2   -1
75	// -Inf  +Inf   -1
76	//
77	// -1.2  -Inf    1
78	// -1.2  -1.2    0
79	// -1.2    -0   -1
80	// -1.2     0   -1
81	// -1.2   1.2   -1
82	// -1.2  +Inf   -1
83	//
84	//   -0  -Inf    1
85	//   -0  -1.2    1
86	//   -0    -0    0
87	//   -0     0    0
88	//   -0   1.2   -1
89	//   -0  +Inf   -1
90	//
91	//    0  -Inf    1
92	//    0  -1.2    1
93	//    0    -0    0
94	//    0     0    0
95	//    0   1.2   -1
96	//    0  +Inf   -1
97	//
98	//  1.2  -Inf    1
99	//  1.2  -1.2    1
100	//  1.2    -0    1
101	//  1.2     0    1
102	//  1.2   1.2    0
103	//  1.2  +Inf   -1
104	//
105	// +Inf  -Inf    1
106	// +Inf  -1.2    1
107	// +Inf    -0    1
108	// +Inf     0    1
109	// +Inf   1.2    1
110	// +Inf  +Inf    0
111}
112
113func ExampleRoundingMode() {
114	operands := []float64{2.6, 2.5, 2.1, -2.1, -2.5, -2.6}
115
116	fmt.Print("   x")
117	for mode := big.ToNearestEven; mode <= big.ToPositiveInf; mode++ {
118		fmt.Printf("  %s", mode)
119	}
120	fmt.Println()
121
122	for _, f64 := range operands {
123		fmt.Printf("%4g", f64)
124		for mode := big.ToNearestEven; mode <= big.ToPositiveInf; mode++ {
125			// sample operands above require 2 bits to represent mantissa
126			// set binary precision to 2 to round them to integer values
127			f := new(big.Float).SetPrec(2).SetMode(mode).SetFloat64(f64)
128			fmt.Printf("  %*g", len(mode.String()), f)
129		}
130		fmt.Println()
131	}
132
133	// Output:
134	//    x  ToNearestEven  ToNearestAway  ToZero  AwayFromZero  ToNegativeInf  ToPositiveInf
135	//  2.6              3              3       2             3              2              3
136	//  2.5              2              3       2             3              2              3
137	//  2.1              2              2       2             3              2              3
138	// -2.1             -2             -2      -2            -3             -3             -2
139	// -2.5             -2             -3      -2            -3             -3             -2
140	// -2.6             -3             -3      -2            -3             -3             -2
141}
142
143func ExampleFloat_Copy() {
144	var x, z big.Float
145
146	x.SetFloat64(1.23)
147	r := z.Copy(&x)
148	fmt.Printf("a) r = %g, z = %g, x = %g, r == z = %v\n", r, &z, &x, r == &z)
149
150	// changing z changes r since they are identical
151	z.SetInt64(42)
152	fmt.Printf("b) r = %g, z = %g, r == z = %v\n", r, &z, r == &z)
153
154	x.SetPrec(1)
155	z.Copy(&x)
156	fmt.Printf("c) z = %g, x = %g, z == x = %v\n", &z, &x, &z == &x)
157
158	// Output:
159	// a) r = 1.23, z = 1.23, x = 1.23, r == z = true
160	// b) r = 42, z = 42, r == z = true
161	// c) z = 1, x = 1, z == x = false
162}
163