code review 156089: Allow optional second expression in slice expressions.

Allow optional second expression in slice expressions.
Built-in function copy.
Addresses issue 203.

[gri, 2009-11-19 01:14:21]

Hello go-dev@google.com,

I'd like you to review the following change.

[gri, 2009-11-19 01:29:57]

Hello rsc, r, iant,

I'd like you to review the following change.

[r, 2009-11-19 01:41:37]

LGTM

http://codereview.appspot.com/156089/diff/1003/6
File doc/go_spec.html (right):

http://codereview.appspot.com/156089/diff/1003/6#newcode2343
doc/go_spec.html:2343: indexes starting at 0 and length equal to the difference
s/the difference//

http://codereview.appspot.com/156089/diff/1003/6#newcode2365
doc/go_spec.html:2365: <code>a[lo :]</code> stands for <code>a[lo :
len(a)]</code>.
s/stands for/is shorthand for/

[iant, 2009-11-19 01:57:56]

LGTM

Besides the below, you have to add copy to the list of predeclared identifiers.

http://codereview.appspot.com/156089/diff/10/1005
File doc/go_spec.html (right):

http://codereview.appspot.com/156089/diff/10/1005#newcode2344
doc/go_spec.html:2344: <code>hi</code>&nbsp;-<code>&nbsp;lo</code>.
Put both &nbsp; inside <code> or put both outside <code>.

http://codereview.appspot.com/156089/diff/10/1005#newcode4221
doc/go_spec.html:4221: of type <code>[]T</code>. The number of arguments copied
is the minimum of
So we are implicitly saying that you can copy between different types which are
not assignment compatible, right?  That's fine with me as long we are clear
about it.

[rsc, 2009-11-19 02:01:15]

http://codereview.appspot.com/156089/diff/10/1005
File doc/go_spec.html (right):

http://codereview.appspot.com/156089/diff/10/1005#newcode2349
doc/go_spec.html:2349: a := [4]int{1, 2, 3, 4, 5};
s/[4]/[5]/

http://codereview.appspot.com/156089/diff/10/1005#newcode2358
doc/go_spec.html:2358: s[0] == 2  // == a[lo + 0]
s/lo/1/ throughout
lo is not defined

http://codereview.appspot.com/156089/diff/10/1005#newcode2360
doc/go_spec.html:2360: s[2] == 4  // == a[lo + 2] == a[hi - 1]
i think == a[hi - 1] is confusing here.
hi is not involved in this computation.

http://codereview.appspot.com/156089/diff/10/1005#newcode4226
doc/go_spec.html:4226: copy(dst []T, src []T) int
copy(dst, src []T) int

http://codereview.appspot.com/156089/diff/10/1005#newcode4237
doc/go_spec.html:4237: n2 := copy(s, s[3:]);   // n2 == 3, s == []int{3, 4, 5,
3, 4, 5}
more interesting example would be (s, s[2:]) which overlaps

[gri, 2009-11-19 02:09:14]

PTAL

http://codereview.appspot.com/156089/diff/10/1005
File doc/go_spec.html (right):

http://codereview.appspot.com/156089/diff/10/1005#newcode2344
doc/go_spec.html:2344: <code>hi</code>&nbsp;-<code>&nbsp;lo</code>.
On 2009/11/19 01:57:56, iant wrote:
> Put both &nbsp; inside <code> or put both outside <code>.
Good catch.

http://codereview.appspot.com/156089/diff/10/1005#newcode2349
doc/go_spec.html:2349: a := [4]int{1, 2, 3, 4, 5};
On 2009/11/19 02:01:15, rsc wrote:
> s/[4]/[5]/
> 
Also a good catch.

http://codereview.appspot.com/156089/diff/10/1005#newcode2358
doc/go_spec.html:2358: s[0] == 2  // == a[lo + 0]
On 2009/11/19 02:01:15, rsc wrote:
> s/lo/1/ throughout
> lo is not defined
> 

Done.

http://codereview.appspot.com/156089/diff/10/1005#newcode2360
doc/go_spec.html:2360: s[2] == 4  // == a[lo + 2] == a[hi - 1]
On 2009/11/19 02:01:15, rsc wrote:
> i think == a[hi - 1] is confusing here.
> hi is not involved in this computation.
> 
Removed comments altogether

http://codereview.appspot.com/156089/diff/10/1005#newcode4221
doc/go_spec.html:4221: of type <code>[]T</code>. The number of arguments copied
is the minimum of
On 2009/11/19 01:57:56, iant wrote:
> So we are implicitly saying that you can copy between different types which
are
> not assignment compatible, right?  That's fine with me as long we are clear
> about it.

I believe that is correct.

http://codereview.appspot.com/156089/diff/10/1005#newcode4226
doc/go_spec.html:4226: copy(dst []T, src []T) int
On 2009/11/19 02:01:15, rsc wrote:
> copy(dst, src []T) int
> 

Done.

http://codereview.appspot.com/156089/diff/10/1005#newcode4237
doc/go_spec.html:4237: n2 := copy(s, s[3:]);   // n2 == 3, s == []int{3, 4, 5,
3, 4, 5}
On 2009/11/19 02:01:15, rsc wrote:
> more interesting example would be (s, s[2:]) which overlaps
> 
I intended to have an overlapping example but changed the sizes. Done.

[iant, 2009-11-19 02:13:26]

LGTM

Still missing copy in list of predeclared identifiers, though, right?

[rsc, 2009-11-19 02:14:34]

LGTM

[gri, 2009-11-19 03:15:31]

*** Submitted as http://code.google.com/p/go/source/detail?r=b8d347e429d9 ***

Allow optional second expression in slice expressions.
Built-in function copy.
Addresses issue 203.

R=rsc, r, iant
http://codereview.appspot.com/156089