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// $G $D/$F.go && $L $F.$A && ./$A.out || echo BUG: bug120

// Copyright 2009 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 main

import "os"

import "strconv"

type Test struct {

        f   float64

        in  string

        out string

}

var tests = []Test{

        Test{123.5, "123.5", "123.5"},

        Test{456.7, "456.7", "456.7"},

        Test{1e23 + 8.5e6, "1e23+8.5e6", "1.0000000000000001e+23"},

        Test{100000000000000008388608, "100000000000000008388608", "1.0000000000000001e+23"},

        Test{1e23 + 8388609, "1e23+8388609", "1.0000000000000001e+23"},

        // "x" = the floating point value from converting the string x.

        // These are exactly representable in 64-bit floating point:

        //      1e23-8388608

        //      1e23+8388608

        // The former has an even mantissa, so "1e23" rounds to 1e23-8388608.

        // If "1e23+8388608" is implemented as "1e23" + "8388608",

        // that ends up computing 1e23-8388608 + 8388608 = 1e23,

        // which rounds back to 1e23-8388608.

        // The correct answer, of course, would be "1e23+8388608" = 1e23+8388608.

        // This is not going to be correct until 6g has multiprecision floating point.

        // A simpler case is "1e23+1", which should also round to 1e23+8388608.

        Test{1e23 + 8.388608e6, "1e23+8.388608e6", "1.0000000000000001e+23"},

        Test{1e23 + 1, "1e23+1", "1.0000000000000001e+23"},

}

func main() {

        ok := true

        for i := 0; i < len(tests); i++ {

                t := tests[i]

                v := strconv.FormatFloat(t.f, 'g', -1, 64)

                if v != t.out {

                        println("Bad float64 const:", t.in, "want", t.out, "got", v)

                        x, err := strconv.ParseFloat(t.out, 64)

                        if err != nil {

                                println("bug120: strconv.Atof64", t.out)

                                panic("fail")

                        }

                        println("\twant exact:", strconv.FormatFloat(x, 'g', 1000, 64))

                        println("\tgot exact: ", strconv.FormatFloat(t.f, 'g', 1000, 64))

                        ok = false

                }

        }

        if !ok {

                os.Exit(1)

        }

}