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big: fix panic and round correctly in Rat.FloatString

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R=gri, rsc
CC=golang-dev
https://golang.org/cl/2212044
This commit is contained in:
Anthony Martin 2010-10-07 16:10:48 +02:00 committed by Robert Griesemer
parent 1f6f563900
commit 5781a00e00
2 changed files with 27 additions and 13 deletions
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35
src/pkg/big/rat.go
View File

@ -294,25 +294,34 @@ func (z *Rat) FloatString(prec int) string {
q, r := nat{}.div(nat{}, z.a.abs, z.b)
p := natOne
if prec > 0 {
p = nat{}.expNN(natTen, nat{}.setUint64(uint64(prec)), nil)
}
r = r.mul(r, p)
r, r2 := r.div(nat{}, r, z.b)
// see if we need to round up
r2 = r2.add(r2, r2)
if z.b.cmp(r2) <= 0 {
r = r.add(r, natOne)
if r.cmp(p) >= 0 {
q = nat{}.add(q, natOne)
r = nat{}.sub(r, p)
}
}
s := q.string(10)
if z.a.neg {
s = "-" + s
}
p := nat{}.expNN(natTen, nat{Word(prec)}, nil)
r = r.mul(r, p)
r, r2 := r.div(nat{}, r, z.b)
// see if we need to round up
r2 = r2.mul(r2, natTwo)
if z.b.cmp(r2) <= 0 {
r = r.add(r, natOne)
if prec > 0 {
rs := r.string(10)
leadingZeros := prec - len(rs)
s += "." + strings.Repeat("0", leadingZeros) + rs
}
rs := r.string(10)
leadingZeros := prec - len(rs)
s += "." + strings.Repeat("0", leadingZeros) + rs
s = strings.TrimRight(s, "0")
return s
}

5
src/pkg/big/rat_test.go
View File

@ -71,6 +71,11 @@ var floatStringTests = []floatStringTest{
floatStringTest{".25", 1, "0.3"},
floatStringTest{"-1/3", 3, "-0.333"},
floatStringTest{"-2/3", 4, "-0.6667"},
floatStringTest{"0.96", 1, "1.0"},
floatStringTest{"0.999", 2, "1.00"},
floatStringTest{"0.9", 0, "1"},
floatStringTest{".25", -1, "0"},
floatStringTest{".55", -1, "1"},
}
func TestFloatString(t *testing.T) {