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strconv: fix %.1f, 0.09

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Fixes #822.
Credit to https://golang.org/cl/1442041 by danielfleischman

R=rsc
CC=golang-dev
https://golang.org/cl/1738047
This commit is contained in:
Rob Pike 2010-06-29 16:51:56 -07:00
parent 21f8ae8fec
commit 64b6a789a1
3 changed files with 21 additions and 6 deletions
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4
src/pkg/strconv/atof_test.go
View File

@ -74,8 +74,10 @@ var atoftests = []atofTest{
atofTest{"1e-322", "1e-322", nil}, atofTest{"1e-322", "1e-322", nil},
// smallest denormal // smallest denormal
atofTest{"5e-324", "5e-324", nil}, atofTest{"5e-324", "5e-324", nil},
atofTest{"4e-324", "5e-324", nil},
atofTest{"3e-324", "5e-324", nil},
// too small // too small
atofTest{"4e-324", "0", nil}, atofTest{"2e-324", "0", nil},
// way too small // way too small
atofTest{"1e-350", "0", nil}, atofTest{"1e-350", "0", nil},
atofTest{"1e-400000", "0", nil}, atofTest{"1e-400000", "0", nil},

13
src/pkg/strconv/decimal.go
View File

@ -289,11 +289,11 @@ func (a *decimal) Shift(k int) *decimal {
// If we chop a at nd digits, should we round up? // If we chop a at nd digits, should we round up?
func shouldRoundUp(a *decimal, nd int) bool { func shouldRoundUp(a *decimal, nd int) bool {
if nd <= 0 || nd >= a.nd { if nd < 0 || nd >= a.nd {
return false return false
} }
if a.d[nd] == '5' && nd+1 == a.nd { // exactly halfway - round to even if a.d[nd] == '5' && nd+1 == a.nd { // exactly halfway - round to even
return (a.d[nd-1]-'0')%2 != 0 return nd > 0 && (a.d[nd-1]-'0')%2 != 0
} }
// not halfway - digit tells all // not halfway - digit tells all
return a.d[nd] >= '5' return a.d[nd] >= '5'
@ -301,8 +301,11 @@ func shouldRoundUp(a *decimal, nd int) bool {
// Round a to nd digits (or fewer). // Round a to nd digits (or fewer).
// Returns receiver for convenience. // Returns receiver for convenience.
// If nd is zero, it means we're rounding
// just to the left of the digits, as in
// 0.09 -> 0.1.
func (a *decimal) Round(nd int) *decimal { func (a *decimal) Round(nd int) *decimal {
if nd <= 0 || nd >= a.nd { if nd < 0 || nd >= a.nd {
return a return a
} }
if shouldRoundUp(a, nd) { if shouldRoundUp(a, nd) {
@ -314,7 +317,7 @@ func (a *decimal) Round(nd int) *decimal {
// Round a down to nd digits (or fewer). // Round a down to nd digits (or fewer).
// Returns receiver for convenience. // Returns receiver for convenience.
func (a *decimal) RoundDown(nd int) *decimal { func (a *decimal) RoundDown(nd int) *decimal {
if nd <= 0 || nd >= a.nd { if nd < 0 || nd >= a.nd {
return a return a
} }
a.nd = nd a.nd = nd
@ -325,7 +328,7 @@ func (a *decimal) RoundDown(nd int) *decimal {
// Round a up to nd digits (or fewer). // Round a up to nd digits (or fewer).
// Returns receiver for convenience. // Returns receiver for convenience.
func (a *decimal) RoundUp(nd int) *decimal { func (a *decimal) RoundUp(nd int) *decimal {
if nd <= 0 || nd >= a.nd { if nd < 0 || nd >= a.nd {
return a return a
} }

10
src/pkg/strconv/ftoa_test.go
View File

@ -108,6 +108,16 @@ var ftoatests = []ftoaTest{
ftoaTest{-math.Inf(0), 'g', -1, "-Inf"}, ftoaTest{-math.Inf(0), 'g', -1, "-Inf"},
ftoaTest{-1, 'b', -1, "-4503599627370496p-52"}, ftoaTest{-1, 'b', -1, "-4503599627370496p-52"},
// fixed bugs
ftoaTest{0.9, 'f', 1, "0.9"},
ftoaTest{0.09, 'f', 1, "0.1"},
ftoaTest{0.0999, 'f', 1, "0.1"},
ftoaTest{0.05, 'f', 1, "0.1"},
ftoaTest{0.05, 'f', 0, "0"},
ftoaTest{0.5, 'f', 1, "0.5"},
ftoaTest{0.5, 'f', 0, "0"},
ftoaTest{1.5, 'f', 0, "2"},
} }
func TestFtoa(t *testing.T) { func TestFtoa(t *testing.T) {