Zen slice on hashes: is %h{} the same as %h{*} or not?

[lizmat]

The zen slice on hashes is currently implemented as:

multi method postcircumfix:<{ }>() { self }

I think it should be implemented as:

multi method postcircumfix:<{ }>() { self.values }

to make it inline with %hash{*}. This would make it consistent with the zen slice of arrays.

And it would make it inline with S03:5161, which states: "The empty C<[]> and C<.[]> postfix operators are interpreted as a zero-dimensional subscript returning the entire array, not as a one-dimensional null slice returning no elements. Likewise for C<{}> and C<.{}> on hashes, as well as the C<< <> >>, C<< .<> >>, C<«»>, and C<.«»> constant and interpolating slice subscripting forms."

So I ran a spectest with %h{} returning the values of the hash, just as %h{*}, and the following spectests failed:

t/spec/S02-literals/hash-interpolation.t (Wstat: 0 Tests: 10 Failed: 2) Failed tests: 5-6 t/spec/S02-literals/misc-interpolation.t (Wstat: 0 Tests: 46 Failed: 1) Failed test: 4 t/spec/S02-literals/quoting.rakudo (Wstat: 0 Tests: 162 Failed: 1) Failed test: 124 t/spec/S02-types/hash.t (Wstat: 256 Tests: 22 Failed: 0) Non-zero exit status: 1 Parse errors: Bad plan. You planned 81 tests but ran 22.

The last one because it was trying to do a sort on *.value, which of course doesn't work on Ints. So from a spec testing point of view, this would be easily fixed.

However, the general feeling on #perl6 was, that the current implementation was the Right Way To Do It. Hence this issue, as the feeling on #perl6 was that the spec should be adapted, rather than the implementation. Which, by the way, is done the same (wrong) way in Niecza.

[Benabik]

The empty [] and .[] postfix operators are interpreted as a zero-dimensional subscript returning the entire array

Simply replacing hash with array there gives "The empty {} and .{} postfix operators are interpreted as a zero-dimensional subscript returning the entire hash." I think the current behavior helps with interpolation where the {} or [] helps separate the array/hash from any following text.

[lizmat]

On Jun 12, 2013, at 4:31 PM, Brian Gernhardt notifications@github.com wrote:

The empty [] and .[] postfix operators are interpreted as a zero-dimensional subscript returning the entire array

Simply replacing hash with array there gives "The empty {} and .{} postfix operators are interpreted as a zero-dimensional subscript returning the entire hash." I think the current behavior helps with interpolation where the {} or [] helps separate the array/hash from any following text.

On the other hand: @a[] could be seen as returning all .values of an array, and so could %h{}.

Liz

[masak]

<TimToady> on zen slices, .[] is supposed to be equivalent to @(), and .{} equivalent to %(), as a convenient contextualizer
<TimToady> .{} is specifically not the same as .{*}
* masak adds that to perl6/specs/issues

I think this issue can be closed now. lizmat?

[lizmat]

Still thinks it could use some more explanation at S03:5161, but I can't think of any right now. So closing.