...

# Source file src/math/big/floatconv_test.go

## Documentation: math/big

```  // Copyright 2015 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style

package big

import (
"bytes"
"fmt"
"math"
"math/bits"
"strconv"
"testing"
)

var zero_ float64

func TestFloatSetFloat64String(t *testing.T) {
inf := math.Inf(0)
nan := math.NaN()

for _, test := range []struct {
s string
x float64 // NaNs represent invalid inputs
}{
// basics
{"0", 0},
{"-0", -zero_},
{"+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", -zero_},
{"+0e-100", 0},
{"0E100", 0},
{"-0E+100", -zero_},
{"+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},

// infinities
{"Inf", inf},
{"+Inf", inf},
{"-Inf", -inf},
{"inf", inf},
{"+inf", inf},
{"-inf", -inf},

// invalid numbers
{"", nan},
{"-", nan},
{"0x", nan},
{"0e", nan},
{"1.2ef", nan},
{"2..3", nan},
{"123..", nan},
{"infinity", nan},
{"foobar", nan},

// 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", -zero_},
{"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", -zero_},
{"0b0e+10", 0},
{"-0b0e-10", -zero_},
{"0b1010", 10},
{"0B1010E2", 1000},
{"0b.1", 0.5},
{"0b.001", 0.125},
{"0b.001e3", 125},

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

{"0x0", 0},
{"-0x0", -zero_},
{"0x0p+10", 0},
{"-0x0p-10", -zero_},
{"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 math.IsNaN(test.x) {
// test.s is invalid
if ok {
t.Errorf("%s: want parse error", test.s)
}
continue
}
// test.s is valid
if !ok {
t.Errorf("%s: got parse error", test.s)
continue
}
f, _ := x.Float64()
want := new(Float).SetFloat64(test.x)
if x.Cmp(want) != 0 || x.Signbit() != want.Signbit() {
t.Errorf("%s: got %v (%v); want %v", test.s, &x, f, test.x)
}
}
}

func fdiv(a, b float64) float64 { return a / b }

const (
below1e23 = 99999999999999974834176
above1e23 = 100000000000000008388608
)

func TestFloat64Text(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"},

{0.001, 'e', 0, "1e-03"},
{0.459, 'e', 0, "5e-01"},
{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"},

{0.001, 'f', 0, "0"},
{0.459, 'f', 0, "0"},
{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.8p+11"},
{-1024.0, 'p', 0, "-0x.8p+11"},

// 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"},

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

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

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

// {math.NaN(), 'g', -1, "NaN"},  // Float doesn't support NaNs
// {-math.NaN(), 'g', -1, "NaN"}, // Float doesn't support NaNs
{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"},

// Issue 15918.
{1, 'f', -10, "1"},
{1, 'f', -11, "1"},
{1, 'f', -12, "1"},
} {
// The test cases are from the strconv package which tests float64 values.
// When formatting values with prec = -1 (shortest representation),
// the actually available mantissa precision matters.
// For denormalized values, that precision is < 53 (SetFloat64 default).
// Compute and set the actual precision explicitly.
f := new(Float).SetPrec(actualPrec(test.x)).SetFloat64(test.x)
got := f.Text(test.format, test.prec)
if got != test.want {
t.Errorf("%v: got %s; want %s", test, got, test.want)
continue
}

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)
}
}
}

// actualPrec returns the number of actually used mantissa bits.
func actualPrec(x float64) uint {
if mant := math.Float64bits(x); x != 0 && mant&(0x7ff<<52) == 0 {
// x is denormalized
}
return 53
}

func TestFloatText(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
{"1e646456992", 64, 'p', 0, "0x.e883a0c5c8c7c42ap+2147483644"},
{"1e646456993", 64, 'p', 0, "+Inf"},
{"1e1000000000", 64, 'p', 0, "+Inf"},
{"1e-1000000", 64, 'p', 0, "0x.efb4542cc8ca418ap-3321928"},
{"1e-646456993", 64, 'p', 0, "0x.e17c8956983d9d59p-2147483647"},
{"1e-646456994", 64, 'p', 0, "0"},
{"1e-1000000000", 64, 'p', 0, "0"},

// minimum and maximum values
{"1p2147483646", 64, 'p', 0, "0x.8p+2147483647"},
{"0x.8p2147483647", 64, 'p', 0, "0x.8p+2147483647"},
{"0x.8p-2147483647", 64, 'p', 0, "0x.8p-2147483647"},
{"1p-2147483649", 64, 'p', 0, "0x.8p-2147483648"},

// 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.cp+2"},
{"03", 350, 'p', 0, "0x.cp+2"},
{"3.", 350, 'p', 0, "0x.cp+2"},
{"3.0", 350, 'p', 0, "0x.cp+2"},
{"3.00", 350, 'p', 0, "0x.cp+2"},
{"3.000", 350, 'p', 0, "0x.cp+2"},

{"0", 64, 'p', 0, "0"},
{"-0", 64, 'p', 0, "-0"},
{"1024.0", 64, 'p', 0, "0x.8p+11"},
{"-1024.0", 64, 'p', 0, "-0x.8p+11"},

// unsupported format
{"3.14", 64, 'x', 0, "%x"},
{"-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.Text(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)
}
}
}
}

func TestFloatFormat(t *testing.T) {
for _, test := range []struct {
format string
value  interface{} // float32, float64, or string (== 512bit *Float)
want   string
}{
// from fmt/fmt_test.go
{"%+.3e", 0.0, "+0.000e+00"},
{"%+.3e", 1.0, "+1.000e+00"},
{"%+.3f", -1.0, "-1.000"},
{"%+.3F", -1.0, "-1.000"},
{"%+.3F", float32(-1.0), "-1.000"},
{"%+07.2f", 1.0, "+001.00"},
{"%+07.2f", -1.0, "-001.00"},
{"%+10.2f", +1.0, "     +1.00"},
{"%+10.2f", -1.0, "     -1.00"},
{"% .3E", -1.0, "-1.000E+00"},
{"% .3e", 1.0, " 1.000e+00"},
{"%+.3g", 0.0, "+0"},
{"%+.3g", 1.0, "+1"},
{"%+.3g", -1.0, "-1"},
{"% .3g", -1.0, "-1"},
{"% .3g", 1.0, " 1"},
{"%b", float32(1.0), "8388608p-23"},
{"%b", 1.0, "4503599627370496p-52"},

// from fmt/fmt_test.go: old test/fmt_test.go
{"%e", 1.0, "1.000000e+00"},
{"%e", 1234.5678e3, "1.234568e+06"},
{"%e", 1234.5678e-8, "1.234568e-05"},
{"%e", -7.0, "-7.000000e+00"},
{"%e", -1e-9, "-1.000000e-09"},
{"%f", 1234.5678e3, "1234567.800000"},
{"%f", 1234.5678e-8, "0.000012"},
{"%f", -7.0, "-7.000000"},
{"%f", -1e-9, "-0.000000"},
{"%g", 1234.5678e3, "1.2345678e+06"},
{"%g", float32(1234.5678e3), "1.2345678e+06"},
{"%g", 1234.5678e-8, "1.2345678e-05"},
{"%g", -7.0, "-7"},
{"%g", -1e-9, "-1e-09"},
{"%g", float32(-1e-9), "-1e-09"},
{"%E", 1.0, "1.000000E+00"},
{"%E", 1234.5678e3, "1.234568E+06"},
{"%E", 1234.5678e-8, "1.234568E-05"},
{"%E", -7.0, "-7.000000E+00"},
{"%E", -1e-9, "-1.000000E-09"},
{"%G", 1234.5678e3, "1.2345678E+06"},
{"%G", float32(1234.5678e3), "1.2345678E+06"},
{"%G", 1234.5678e-8, "1.2345678E-05"},
{"%G", -7.0, "-7"},
{"%G", -1e-9, "-1E-09"},
{"%G", float32(-1e-9), "-1E-09"},

{"%20.6e", 1.2345e3, "        1.234500e+03"},
{"%20.6e", 1.2345e-3, "        1.234500e-03"},
{"%20e", 1.2345e3, "        1.234500e+03"},
{"%20e", 1.2345e-3, "        1.234500e-03"},
{"%20.8e", 1.2345e3, "      1.23450000e+03"},
{"%20f", 1.23456789e3, "         1234.567890"},
{"%20f", 1.23456789e-3, "            0.001235"},
{"%20f", 12345678901.23456789, "  12345678901.234568"},
{"%-20f", 1.23456789e3, "1234.567890         "},
{"%20.8f", 1.23456789e3, "       1234.56789000"},
{"%20.8f", 1.23456789e-3, "          0.00123457"},
{"%g", 1.23456789e3, "1234.56789"},
{"%g", 1.23456789e-3, "0.00123456789"},
{"%g", 1.23456789e20, "1.23456789e+20"},
{"%20e", math.Inf(1), "                +Inf"},
{"%-20f", math.Inf(-1), "-Inf                "},

// from fmt/fmt_test.go: comparison of padding rules with C printf
{"%.2f", 1.0, "1.00"},
{"%.2f", -1.0, "-1.00"},
{"% .2f", 1.0, " 1.00"},
{"% .2f", -1.0, "-1.00"},
{"%+.2f", 1.0, "+1.00"},
{"%+.2f", -1.0, "-1.00"},
{"%7.2f", 1.0, "   1.00"},
{"%7.2f", -1.0, "  -1.00"},
{"% 7.2f", 1.0, "   1.00"},
{"% 7.2f", -1.0, "  -1.00"},
{"%+7.2f", 1.0, "  +1.00"},
{"%+7.2f", -1.0, "  -1.00"},
{"%07.2f", 1.0, "0001.00"},
{"%07.2f", -1.0, "-001.00"},
{"% 07.2f", 1.0, " 001.00"},
{"% 07.2f", -1.0, "-001.00"},
{"%+07.2f", 1.0, "+001.00"},
{"%+07.2f", -1.0, "-001.00"},

// from fmt/fmt_test.go: zero padding does not apply to infinities
{"%020f", math.Inf(-1), "                -Inf"},
{"%020f", math.Inf(+1), "                +Inf"},
{"% 020f", math.Inf(-1), "                -Inf"},
{"% 020f", math.Inf(+1), "                 Inf"},
{"%+020f", math.Inf(-1), "                -Inf"},
{"%+020f", math.Inf(+1), "                +Inf"},
{"%20f", -1.0, "           -1.000000"},

// handle %v like %g
{"%v", 0.0, "0"},
{"%v", -7.0, "-7"},
{"%v", -1e-9, "-1e-09"},
{"%v", float32(-1e-9), "-1e-09"},
{"%010v", 0.0, "0000000000"},

// *Float cases
{"%.20f", "1e-20", "0.00000000000000000001"},
{"%.20f", "-1e-20", "-0.00000000000000000001"},
{"%30.20f", "-1e-20", "       -0.00000000000000000001"},
{"%030.20f", "-1e-20", "-00000000.00000000000000000001"},
{"%030.20f", "+1e-20", "000000000.00000000000000000001"},
{"% 030.20f", "+1e-20", " 00000000.00000000000000000001"},

// erroneous formats
{"%s", 1.0, "%!s(*big.Float=1)"},
} {
value := new(Float)
switch v := test.value.(type) {
case float32:
value.SetPrec(24).SetFloat64(float64(v))
case float64:
value.SetPrec(53).SetFloat64(v)
case string:
value.SetPrec(512).Parse(v, 0)
default:
t.Fatalf("unsupported test value: %v (%T)", v, v)
}

if got := fmt.Sprintf(test.format, value); got != test.want {
t.Errorf("%v: got %q; want %q", test, got, test.want)
}
}
}

func BenchmarkParseFloatSmallExp(b *testing.B) {
for i := 0; i < b.N; i++ {
for _, s := range []string{
"1e0",
"1e-1",
"1e-2",
"1e-3",
"1e-4",
"1e-5",
"1e-10",
"1e-20",
"1e-50",
"1e1",
"1e2",
"1e3",
"1e4",
"1e5",
"1e10",
"1e20",
"1e50",
} {
var x Float
_, _, err := x.Parse(s, 0)
if err != nil {
b.Fatalf("%s: %v", s, err)
}
}
}
}

func BenchmarkParseFloatLargeExp(b *testing.B) {
for i := 0; i < b.N; i++ {
for _, s := range []string{
"1e0",
"1e-10",
"1e-20",
"1e-30",
"1e-40",
"1e-50",
"1e-100",
"1e-500",
"1e-1000",
"1e-5000",
"1e-10000",
"1e10",
"1e20",
"1e30",
"1e40",
"1e50",
"1e100",
"1e500",
"1e1000",
"1e5000",
"1e10000",
} {
var x Float
_, _, err := x.Parse(s, 0)
if err != nil {
b.Fatalf("%s: %v", s, err)
}
}
}
}

func TestFloatScan(t *testing.T) {
var floatScanTests = []struct {
input     string
format    string
output    string
remaining int
wantErr   bool
}{
0: {"10.0", "%f", "10", 0, false},
1: {"23.98+2.0", "%v", "23.98", 4, false},
2: {"-1+1", "%v", "-1", 2, false},
3: {" 00000", "%v", "0", 0, false},
4: {"-123456p-78", "%b", "-4.084816388e-19", 0, false},
5: {"+123", "%b", "123", 0, false},
6: {"-1.234e+56", "%e", "-1.234e+56", 0, false},
7: {"-1.234E-56", "%E", "-1.234e-56", 0, false},
8: {"-1.234e+567", "%g", "-1.234e+567", 0, false},
9: {"+1234567891011.234", "%G", "1.234567891e+12", 0, false},

// Scan doesn't handle ±Inf.
10: {"Inf", "%v", "", 3, true},
11: {"-Inf", "%v", "", 3, true},
12: {"-Inf", "%v", "", 3, true},
}

var buf bytes.Buffer
for i, test := range floatScanTests {
x := new(Float)
buf.Reset()
buf.WriteString(test.input)
_, err := fmt.Fscanf(&buf, test.format, x)
if test.wantErr {
if err == nil {
t.Errorf("#%d want non-nil err", i)
}
continue
}

if err != nil {
t.Errorf("#%d error: %s", i, err)
}

if x.String() != test.output {
t.Errorf("#%d got %s; want %s", i, x.String(), test.output)
}
if buf.Len() != test.remaining {
t.Errorf("#%d got %d bytes remaining; want %d", i, buf.Len(), test.remaining)
}
}
}

```

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