github.com/rsc/go@v0.0.0-20150416155037-e040fd465409/src/math/big/floatconv_test.go

// 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

import (
	"math"
	"strconv"
	"testing"
)

func TestFloatSetFloat64String(t *testing.T) {
	for _, test := range []struct {
		s string
		x float64
	}{
		// basics
		{"0", 0},
		{"-0", -0},
		{"+0", 0},
		{"1", 1},
		{"-1", -1},
		{"+1", 1},
		{"1.234", 1.234},
		{"-1.234", -1.234},
		{"+1.234", 1.234},
		{".1", 0.1},
		{"1.", 1},
		{"+1.", 1},

		// various zeros
		{"0e100", 0},
		{"-0e+100", 0},
		{"+0e-100", 0},
		{"0E100", 0},
		{"-0E+100", 0},
		{"+0E-100", 0},

		// various decimal exponent formats
		{"1.e10", 1e10},
		{"1e+10", 1e10},
		{"+1e-10", 1e-10},
		{"1E10", 1e10},
		{"1.E+10", 1e10},
		{"+1E-10", 1e-10},

		// misc decimal values
		{"3.14159265", 3.14159265},
		{"-687436.79457e-245", -687436.79457e-245},
		{"-687436.79457E245", -687436.79457e245},
		{".0000000000000000000000000000000000000001", 1e-40},
		{"+10000000000000000000000000000000000000000e-0", 1e40},

		// decimal mantissa, binary exponent
		{"0p0", 0},
		{"-0p0", -0},
		{"1p10", 1 << 10},
		{"1p+10", 1 << 10},
		{"+1p-10", 1.0 / (1 << 10)},
		{"1024p-12", 0.25},
		{"-1p10", -1024},
		{"1.5p1", 3},

		// binary mantissa, decimal exponent
		{"0b0", 0},
		{"-0b0", -0},
		{"0b0e+10", 0},
		{"-0b0e-10", -0},
		{"0b1010", 10},
		{"0B1010E2", 1000},
		{"0b.1", 0.5},
		{"0b.001", 0.125},
		{"0b.001e3", 125},

		// binary mantissa, binary exponent
		{"0b0p+10", 0},
		{"-0b0p-10", -0},
		{"0b.1010p4", 10},
		{"0b1p-1", 0.5},
		{"0b001p-3", 0.125},
		{"0b.001p3", 1},
		{"0b0.01p2", 1},

		// hexadecimal mantissa and exponent
		{"0x0", 0},
		{"-0x0", -0},
		{"0x0p+10", 0},
		{"-0x0p-10", -0},
		{"0xff", 255},
		{"0X.8p1", 1},
		{"-0X0.00008p16", -0.5},
		{"0x0.0000000000001p-1022", math.SmallestNonzeroFloat64},
		{"0x1.fffffffffffffp1023", math.MaxFloat64},
	} {
		var x Float
		x.SetPrec(53)
		_, ok := x.SetString(test.s)
		if !ok {
			t.Errorf("%s: parse error", test.s)
			continue
		}
		f, _ := x.Float64()
		want := new(Float).SetFloat64(test.x)
		if x.Cmp(want) != 0 {
			t.Errorf("%s: got %s (%v); want %v", test.s, &x, f, test.x)
		}
	}
}

const (
	below1e23 = 99999999999999974834176
	above1e23 = 100000000000000008388608
)

func TestFloat64Format(t *testing.T) {
	for _, test := range []struct {
		x      float64
		format byte
		prec   int
		want   string
	}{
		{0, 'f', 0, "0"},
		{math.Copysign(0, -1), 'f', 0, "-0"},
		{1, 'f', 0, "1"},
		{-1, 'f', 0, "-1"},

		{1.459, 'e', 0, "1e+00"},
		{2.459, 'e', 1, "2.5e+00"},
		{3.459, 'e', 2, "3.46e+00"},
		{4.459, 'e', 3, "4.459e+00"},
		{5.459, 'e', 4, "5.4590e+00"},

		{1.459, 'f', 0, "1"},
		{2.459, 'f', 1, "2.5"},
		{3.459, 'f', 2, "3.46"},
		{4.459, 'f', 3, "4.459"},
		{5.459, 'f', 4, "5.4590"},

		{0, 'b', 0, "0"},
		{math.Copysign(0, -1), 'b', 0, "-0"},
		{1.0, 'b', 0, "4503599627370496p-52"},
		{-1.0, 'b', 0, "-4503599627370496p-52"},
		{4503599627370496, 'b', 0, "4503599627370496p+0"},

		{0, 'p', 0, "0"},
		{math.Copysign(0, -1), 'p', 0, "-0"},
		{1024.0, 'p', 0, "0x.8p11"},
		{-1024.0, 'p', 0, "-0x.8p11"},

		// all test cases below from strconv/ftoa_test.go
		{1, 'e', 5, "1.00000e+00"},
		{1, 'f', 5, "1.00000"},
		{1, 'g', 5, "1"},
		// {1, 'g', -1, "1"},
		// {20, 'g', -1, "20"},
		// {1234567.8, 'g', -1, "1.2345678e+06"},
		// {200000, 'g', -1, "200000"},
		// {2000000, 'g', -1, "2e+06"},

		// g conversion and zero suppression
		{400, 'g', 2, "4e+02"},
		{40, 'g', 2, "40"},
		{4, 'g', 2, "4"},
		{.4, 'g', 2, "0.4"},
		{.04, 'g', 2, "0.04"},
		{.004, 'g', 2, "0.004"},
		{.0004, 'g', 2, "0.0004"},
		{.00004, 'g', 2, "4e-05"},
		{.000004, 'g', 2, "4e-06"},

		{0, 'e', 5, "0.00000e+00"},
		{0, 'f', 5, "0.00000"},
		{0, 'g', 5, "0"},
		// {0, 'g', -1, "0"},

		{-1, 'e', 5, "-1.00000e+00"},
		{-1, 'f', 5, "-1.00000"},
		{-1, 'g', 5, "-1"},
		// {-1, 'g', -1, "-1"},

		{12, 'e', 5, "1.20000e+01"},
		{12, 'f', 5, "12.00000"},
		{12, 'g', 5, "12"},
		// {12, 'g', -1, "12"},

		{123456700, 'e', 5, "1.23457e+08"},
		{123456700, 'f', 5, "123456700.00000"},
		{123456700, 'g', 5, "1.2346e+08"},
		// {123456700, 'g', -1, "1.234567e+08"},

		{1.2345e6, 'e', 5, "1.23450e+06"},
		{1.2345e6, 'f', 5, "1234500.00000"},
		{1.2345e6, 'g', 5, "1.2345e+06"},

		{1e23, 'e', 17, "9.99999999999999916e+22"},
		{1e23, 'f', 17, "99999999999999991611392.00000000000000000"},
		{1e23, 'g', 17, "9.9999999999999992e+22"},

		// {1e23, 'e', -1, "1e+23"},
		// {1e23, 'f', -1, "100000000000000000000000"},
		// {1e23, 'g', -1, "1e+23"},

		{below1e23, 'e', 17, "9.99999999999999748e+22"},
		{below1e23, 'f', 17, "99999999999999974834176.00000000000000000"},
		{below1e23, 'g', 17, "9.9999999999999975e+22"},

		// {below1e23, 'e', -1, "9.999999999999997e+22"},
		// {below1e23, 'f', -1, "99999999999999970000000"},
		// {below1e23, 'g', -1, "9.999999999999997e+22"},

		{above1e23, 'e', 17, "1.00000000000000008e+23"},
		{above1e23, 'f', 17, "100000000000000008388608.00000000000000000"},
		// {above1e23, 'g', 17, "1.0000000000000001e+23"},

		// {above1e23, 'e', -1, "1.0000000000000001e+23"},
		// {above1e23, 'f', -1, "100000000000000010000000"},
		// {above1e23, 'g', -1, "1.0000000000000001e+23"},

		// {fdiv(5e-304, 1e20), 'g', -1, "5e-324"},
		// {fdiv(-5e-304, 1e20), 'g', -1, "-5e-324"},

		// {32, 'g', -1, "32"},
		// {32, 'g', 0, "3e+01"},

		// {100, 'x', -1, "%x"},

		// {math.NaN(), 'g', -1, "NaN"},
		// {-math.NaN(), 'g', -1, "NaN"},
		{math.Inf(0), 'g', -1, "+Inf"},
		{math.Inf(-1), 'g', -1, "-Inf"},
		{-math.Inf(0), 'g', -1, "-Inf"},

		{-1, 'b', -1, "-4503599627370496p-52"},

		// fixed bugs
		{0.9, 'f', 1, "0.9"},
		{0.09, 'f', 1, "0.1"},
		{0.0999, 'f', 1, "0.1"},
		{0.05, 'f', 1, "0.1"},
		{0.05, 'f', 0, "0"},
		{0.5, 'f', 1, "0.5"},
		{0.5, 'f', 0, "0"},
		{1.5, 'f', 0, "2"},

		// http://www.exploringbinary.com/java-hangs-when-converting-2-2250738585072012e-308/
		// {2.2250738585072012e-308, 'g', -1, "2.2250738585072014e-308"},
		// http://www.exploringbinary.com/php-hangs-on-numeric-value-2-2250738585072011e-308/
		// {2.2250738585072011e-308, 'g', -1, "2.225073858507201e-308"},

		// Issue 2625.
		{383260575764816448, 'f', 0, "383260575764816448"},
		// {383260575764816448, 'g', -1, "3.8326057576481645e+17"},
	} {
		f := new(Float).SetFloat64(test.x)
		got := f.Format(test.format, test.prec)
		if got != test.want {
			t.Errorf("%v: got %s; want %s", test, got, test.want)
		}

		if test.format == 'b' && test.x == 0 {
			continue // 'b' format in strconv.Float requires knowledge of bias for 0.0
		}
		if test.format == 'p' {
			continue // 'p' format not supported in strconv.Format
		}

		// verify that Float format matches strconv format
		want := strconv.FormatFloat(test.x, test.format, test.prec, 64)
		if got != want {
			t.Errorf("%v: got %s; want %s (strconv)", test, got, want)
		}
	}
}

func TestFloatFormat(t *testing.T) {
	for _, test := range []struct {
		x      string
		prec   uint
		format byte
		digits int
		want   string
	}{
		{"0", 10, 'f', 0, "0"},
		{"-0", 10, 'f', 0, "-0"},
		{"1", 10, 'f', 0, "1"},
		{"-1", 10, 'f', 0, "-1"},

		{"1.459", 100, 'e', 0, "1e+00"},
		{"2.459", 100, 'e', 1, "2.5e+00"},
		{"3.459", 100, 'e', 2, "3.46e+00"},
		{"4.459", 100, 'e', 3, "4.459e+00"},
		{"5.459", 100, 'e', 4, "5.4590e+00"},

		{"1.459", 100, 'E', 0, "1E+00"},
		{"2.459", 100, 'E', 1, "2.5E+00"},
		{"3.459", 100, 'E', 2, "3.46E+00"},
		{"4.459", 100, 'E', 3, "4.459E+00"},
		{"5.459", 100, 'E', 4, "5.4590E+00"},

		{"1.459", 100, 'f', 0, "1"},
		{"2.459", 100, 'f', 1, "2.5"},
		{"3.459", 100, 'f', 2, "3.46"},
		{"4.459", 100, 'f', 3, "4.459"},
		{"5.459", 100, 'f', 4, "5.4590"},

		{"1.459", 100, 'g', 0, "1"},
		{"2.459", 100, 'g', 1, "2"},
		{"3.459", 100, 'g', 2, "3.5"},
		{"4.459", 100, 'g', 3, "4.46"},
		{"5.459", 100, 'g', 4, "5.459"},

		{"1459", 53, 'g', 0, "1e+03"},
		{"2459", 53, 'g', 1, "2e+03"},
		{"3459", 53, 'g', 2, "3.5e+03"},
		{"4459", 53, 'g', 3, "4.46e+03"},
		{"5459", 53, 'g', 4, "5459"},

		{"1459", 53, 'G', 0, "1E+03"},
		{"2459", 53, 'G', 1, "2E+03"},
		{"3459", 53, 'G', 2, "3.5E+03"},
		{"4459", 53, 'G', 3, "4.46E+03"},
		{"5459", 53, 'G', 4, "5459"},

		{"3", 10, 'e', 40, "3.0000000000000000000000000000000000000000e+00"},
		{"3", 10, 'f', 40, "3.0000000000000000000000000000000000000000"},
		{"3", 10, 'g', 40, "3"},

		{"3e40", 100, 'e', 40, "3.0000000000000000000000000000000000000000e+40"},
		{"3e40", 100, 'f', 4, "30000000000000000000000000000000000000000.0000"},
		{"3e40", 100, 'g', 40, "3e+40"},

		// make sure "stupid" exponents don't stall the machine
		{"1e1000000", 64, 'p', 0, "0x.88b3a28a05eade3ap3321929"},
		{"1e1000000000", 64, 'p', 0, "0x.ecc5f45aa573d3p1538481529"},
		{"1e-1000000", 64, 'p', 0, "0x.efb4542cc8ca418ap-3321928"},
		{"1e-1000000000", 64, 'p', 0, "0x.8a64dd983a4c7dabp-1538481528"},

		// TODO(gri) need tests for actual large Floats

		{"0", 53, 'b', 0, "0"},
		{"-0", 53, 'b', 0, "-0"},
		{"1.0", 53, 'b', 0, "4503599627370496p-52"},
		{"-1.0", 53, 'b', 0, "-4503599627370496p-52"},
		{"4503599627370496", 53, 'b', 0, "4503599627370496p+0"},

		// issue 9939
		{"3", 350, 'b', 0, "1720123961992553633708115671476565205597423741876210842803191629540192157066363606052513914832594264915968p-348"},
		{"03", 350, 'b', 0, "1720123961992553633708115671476565205597423741876210842803191629540192157066363606052513914832594264915968p-348"},
		{"3.", 350, 'b', 0, "1720123961992553633708115671476565205597423741876210842803191629540192157066363606052513914832594264915968p-348"},
		{"3.0", 350, 'b', 0, "1720123961992553633708115671476565205597423741876210842803191629540192157066363606052513914832594264915968p-348"},
		{"3.00", 350, 'b', 0, "1720123961992553633708115671476565205597423741876210842803191629540192157066363606052513914832594264915968p-348"},
		{"3.000", 350, 'b', 0, "1720123961992553633708115671476565205597423741876210842803191629540192157066363606052513914832594264915968p-348"},

		{"3", 350, 'p', 0, "0x.cp2"},
		{"03", 350, 'p', 0, "0x.cp2"},
		{"3.", 350, 'p', 0, "0x.cp2"},
		{"3.0", 350, 'p', 0, "0x.cp2"},
		{"3.00", 350, 'p', 0, "0x.cp2"},
		{"3.000", 350, 'p', 0, "0x.cp2"},

		{"0", 64, 'p', 0, "0"},
		{"-0", 64, 'p', 0, "-0"},
		{"1024.0", 64, 'p', 0, "0x.8p11"},
		{"-1024.0", 64, 'p', 0, "-0x.8p11"},

		// unsupported format
		{"3.14", 64, 'x', 0, "%x"},
	} {
		f, _, err := ParseFloat(test.x, 0, test.prec, ToNearestEven)
		if err != nil {
			t.Errorf("%v: %s", test, err)
			continue
		}

		got := f.Format(test.format, test.digits)
		if got != test.want {
			t.Errorf("%v: got %s; want %s", test, got, test.want)
		}

		// compare with strconv.FormatFloat output if possible
		// ('p' format is not supported by strconv.FormatFloat,
		// and its output for 0.0 prints a biased exponent value
		// as in 0p-1074 which makes no sense to emulate here)
		if test.prec == 53 && test.format != 'p' && f.Sign() != 0 {
			f64, acc := f.Float64()
			if acc != Exact {
				t.Errorf("%v: expected exact conversion to float64", test)
				continue
			}
			got := strconv.FormatFloat(f64, test.format, test.digits, 64)
			if got != test.want {
				t.Errorf("%v: got %s; want %s", test, got, test.want)
			}
		}
	}
}