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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-16 19:25:22 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-16 19:25:22 +0000 |
commit | f6ad4dcef54c5ce997a4bad5a6d86de229015700 (patch) | |
tree | 7cfa4e31ace5c2bd95c72b154d15af494b2bcbef /test/fixedbugs/bug120.go | |
parent | Initial commit. (diff) | |
download | golang-1.22-f6ad4dcef54c5ce997a4bad5a6d86de229015700.tar.xz golang-1.22-f6ad4dcef54c5ce997a4bad5a6d86de229015700.zip |
Adding upstream version 1.22.1.upstream/1.22.1
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'test/fixedbugs/bug120.go')
-rw-r--r-- | test/fixedbugs/bug120.go | 60 |
1 files changed, 60 insertions, 0 deletions
diff --git a/test/fixedbugs/bug120.go b/test/fixedbugs/bug120.go new file mode 100644 index 0000000..58355e5 --- /dev/null +++ b/test/fixedbugs/bug120.go @@ -0,0 +1,60 @@ +// run + +// 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) + } +} |