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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)
        }
}