code review 3352041: big: fix (*Rat) SetFrac64(a, b) when b < 0.

big: fix (*Rat) SetFrac64(a, b) when b < 0.

[ejsherry, 2010-11-29 23:02:12]

Hello gri (cc: golang-dev@googlegroups.com),

I'd like you to review this change.

[gri, 2010-11-30 18:12:18]

LGTM
thanks.
- gri

On Mon, Nov 29, 2010 at 3:02 PM, <ejsherry@gmail.com> wrote:

> Reviewers: gri,
>
> Message:
> Hello gri (cc: golang-dev@googlegroups.com),
>
> I'd like you to review this change.
>
>
> Description:
> big: fix (*Rat) SetFrac64(a, b) when b < 0.
>
> Please review this at http://codereview.appspot.com/3352041/
>
> Affected files:
>  M src/pkg/big/rat.go
>  M src/pkg/big/rat_test.go
>
>
> Index: src/pkg/big/rat.go
> ===================================================================
> --- a/src/pkg/big/rat.go
> +++ b/src/pkg/big/rat.go
> @@ -35,9 +35,8 @@
>  func (z *Rat) SetFrac64(a, b int64) *Rat {
>        z.a.SetInt64(a)
>        if b < 0 {
> -               z.b.setUint64(uint64(-b))
> +               b = -b
>                z.a.neg = !z.a.neg
> -               return z.norm()
>        }
>        z.b = z.b.setUint64(uint64(b))
>        return z.norm()
> Index: src/pkg/big/rat_test.go
> ===================================================================
> --- a/src/pkg/big/rat_test.go
> +++ b/src/pkg/big/rat_test.go
> @@ -257,3 +257,26 @@
>                t.Errorf("got %s want %s", z, q)
>        }
>  }
> +
> +
> +var setFrac64Tests = []struct {
> +       a, b int64
> +       out  string
> +}{
> +       {0, 1, "0"},
> +       {0, -1, "0"},
> +       {1, 1, "1"},
> +       {-1, 1, "-1"},
> +       {1, -1, "-1"},
> +       {-1, -1, "1"},
> +       {-9223372036854775808, -9223372036854775808, "1"},
> +}
> +
> +func TestRatSetFrac64Rat(t *testing.T) {
> +       for i, test := range setFrac64Tests {
> +               x := new(Rat).SetFrac64(test.a, test.b)
> +               if x.RatString() != test.out {
> +                       t.Errorf("#%d got %s want %s", i, x.RatString(),
> test.out)
> +               }
> +       }
> +}
>
>
>

[gri, 2010-11-30 18:23:29]

*** Submitted as http://code.google.com/p/go/source/detail?r=90a6dee6537e ***

big: fix (*Rat) SetFrac64(a, b) when b < 0.

R=gri
CC=golang-dev
http://codereview.appspot.com/3352041

Committer: Robert Griesemer <gri@golang.org>