code review 5465044: time: new AddDate method

time: new AddDate method

[rog, 2011-12-08 13:13:39]

Hello golang-dev@googlegroups.com,

I'd like you to review this change to
https://go.googlecode.com/hg/

[rog, 2011-12-08 13:16:04]

BTW, at first i had a test that t.AddDate(a, b, c).AddDate(-a, -b, c) == t
but that doesn't always work. i suppose it's obvious in retrospect,
but perhaps it deserves a comment?

On 8 December 2011 13:13,  <rogpeppe@gmail.com> wrote:
> Reviewers: golang-dev_googlegroups.com,
>
> Message:
> Hello golang-dev@googlegroups.com,
>
> I'd like you to review this change to
> https://go.googlecode.com/hg/
>
>
> Description:
> time: new AddDate method
>
> Please review this at http://codereview.appspot.com/5465044/
>
> Affected files:
>  M src/pkg/time/time.go
>  M src/pkg/time/time_test.go
>
>
> Index: src/pkg/time/time.go
> ===================================================================
> --- a/src/pkg/time/time.go
> +++ b/src/pkg/time/time.go
> @@ -564,6 +564,20 @@
>        return Duration(t.sec-u.sec)*Second + Duration(t.nsec-u.nsec)
>  }
>
> +// AddDate returns the time corresponding to adding the
> +// given number of years, months, and days to t.
> +// For example, AddDate(-1, 2, 3) applied to January 1, 2011
> +// returns March 4, 2010.
> +//
> +// AddDate normalizes its result in the same way that Date does,
> +// so, for example, adding one month to October 31 yields
> +// December 1, the normalized form for November 31.
> +func (t Time) AddDate(years int, months int, days int) Time {
> +       year, month, day := t.Date()
> +       hour, min, sec := t.Clock()
> +       return Date(year+years, month+Month(months), day+days, hour, min,
> sec, int(t.nsec), t.loc)
> +}
> +
>  const (
>        secondsPerMinute = 60
>        secondsPerHour   = 60 * 60
> Index: src/pkg/time/time_test.go
> ===================================================================
> --- a/src/pkg/time/time_test.go
> +++ b/src/pkg/time/time_test.go
> @@ -632,6 +632,32 @@
>        }
>  }
>
> +// Several ways of getting from
> +// Fri Nov 18 7:56:35 PST 2011
> +// to
> +// Thu Mar 19 7:56:35 PST 2016
> +var addDateTests = []struct {
> +       years, months, days int
> +}{
> +       {4, 4, 1},
> +       {3, 16, 1},
> +       {3, 15, 30},
> +       {5, -6, -18 - 30 - 12},
> +}
> +
> +func TestAddDate(t *testing.T) {
> +       t0 := Date(2011, 11, 18, 7, 56, 35, 0, UTC)
> +       t1 := Date(2016, 3, 19, 7, 56, 35, 0, UTC)
> +       for _, at := range addDateTests {
> +               time := t0.AddDate(at.years, at.months, at.days)
> +               if !time.Equal(t1) {
> +                       t.Errorf("AddDate(%d, %d, %d) = %v, want %v",
> +                               at.years, at.months, at.days,
> +                               time, t1)
> +               }
> +       }
> +}
> +
>  func BenchmarkNow(b *testing.B) {
>        for i := 0; i < b.N; i++ {
>                Now()
>
>

[rsc, 2011-12-08 22:53:37]

On Thu, Dec 8, 2011 at 08:16, roger peppe <rogpeppe@gmail.com> wrote:
> BTW, at first i had a test that t.AddDate(a, b, c).AddDate(-a, -b, c) == t
> but that doesn't always work. i suppose it's obvious in retrospect,
> but perhaps it deserves a comment?

The normalization comment should suffice.  I don't want to
spend more ink on the special cases than on the behavior.

Russ

[rog, 2011-12-14 13:39:16]

ping

On 8 December 2011 22:53, Russ Cox <rsc@golang.org> wrote:

> On Thu, Dec 8, 2011 at 08:16, roger peppe <rogpeppe@gmail.com> wrote:
> > BTW, at first i had a test that t.AddDate(a, b, c).AddDate(-a, -b, c) ==
> t
> > but that doesn't always work. i suppose it's obvious in retrospect,
> > but perhaps it deserves a comment?
>
> The normalization comment should suffice.  I don't want to
> spend more ink on the special cases than on the behavior.
>
> Russ
>

[rsc, 2011-12-15 16:14:09]

LGTM

[rsc, 2011-12-15 16:23:06]

*** Submitted as http://code.google.com/p/go/source/detail?r=50e6f6bb7af5 ***

time: new AddDate method

R=rsc
CC=golang-dev
http://codereview.appspot.com/5465044

Committer: Russ Cox <rsc@golang.org>