substr on compact array

[p6rt]

Migrated from rt.perl.org#124455 (status was 'open')

Searchable as RT124455$

[p6rt]

From @coke

3 tests here that need fixing or review​:

  my uint8 @​buffer = ('A' .. 'Z').map({ .ord });
  is(substr(@​buffer, 0, 8), ord('A'), 'substr on compact array (1)');
  is(substr(@​buffer, 200, 8), ord('Z'), 'substr on compact array (2)');
  is(
  substr(@​buffer, 0, 16),
  sprintf('%08d%08d', ord('A'), ord('B')),
  'substr on compacy array (3)'
  );

yields​:

# Failed test 'substr on compact array (1)'
# at t/spec/S02-types/compact.rakudo.moar line 14
# expected​: '65'
# got​: '65 66 67'
# Failed test 'substr on compact array (2)'
# at t/spec/S02-types/compact.rakudo.moar line 15
# expected​: '90'
# got​: (Failure)
# Failed test 'substr on compacy array (3)'
# at t/spec/S02-types/compact.rakudo.moar line 16
# expected​: '0000006500000066'
# got​: '65 66 67 68 69 7'

--
Will "Coke" Coleda

[p6rt]

From @coke

3 tests here that need fixing or review​:

  my uint8 @​buffer = ('A' .. 'Z').map({ .ord });
  is(substr(@​buffer, 0, 8), ord('A'), 'substr on compact array (1)');
  is(substr(@​buffer, 200, 8), ord('Z'), 'substr on compact array (2)');
  is(
  substr(@​buffer, 0, 16),
  sprintf('%08d%08d', ord('A'), ord('B')),
  'substr on compacy array (3)'
  );

yields​:

# Failed test 'substr on compact array (1)'
# at t/spec/S02-types/compact.rakudo.moar line 14
# expected​: '65'
# got​: '65 66 67'
# Failed test 'substr on compact array (2)'
# at t/spec/S02-types/compact.rakudo.moar line 15
# expected​: '90'
# got​: (Failure)
# Failed test 'substr on compacy array (3)'
# at t/spec/S02-types/compact.rakudo.moar line 16
# expected​: '0000006500000066'
# got​: '65 66 67 68 69 7'

--
Will "Coke" Coleda

[p6rt]

From @AlexDaniel

Oh wow, that's really interesting… and old.

I don't think that substr should work like this. Normal arrays are stringified by ｢substr｣, why would it do something completely different for a native array? So for both UInt and uint8 arrays I'd expect “65 66 67” as an output.

I think this ticket is rejectable as soon as someone can justify it better than me.

On 2015-05-12 09​:54​:38, coke wrote​:

3 tests here that need fixing or review​:

my uint8 @​buffer = ('A' .. 'Z').map({ .ord });
is(substr(@​buffer, 0, 8), ord('A'), 'substr on compact array (1)');
is(substr(@​buffer, 200, 8), ord('Z'), 'substr on compact array (2)');
is(
substr(@​buffer, 0, 16),
sprintf('%08d%08d', ord('A'), ord('B')),
'substr on compacy array (3)'
);

yields​:

# Failed test 'substr on compact array (1)'
# at t/spec/S02-types/compact.rakudo.moar line 14
# expected​: '65'
# got​: '65 66 67'
# Failed test 'substr on compact array (2)'
# at t/spec/S02-types/compact.rakudo.moar line 15
# expected​: '90'
# got​: (Failure)
# Failed test 'substr on compacy array (3)'
# at t/spec/S02-types/compact.rakudo.moar line 16
# expected​: '0000006500000066'
# got​: '65 66 67 68 69 7'

[p6rt]

The RT System itself - Status changed from 'new' to 'open'

[p6rt]

From @timo

The tests are bogus just the assumption that a substr of length 8 will give you 8 bits rather than 8 bytes, that's already wildly inconsistent with what substr does otherwise.

really this code looks like the desire to have `vec` from perl5 implemented in perl6 by re-using the substr name. I think it's the wrong peg to hang this feature off of.

[p6rt]

From @timo

Also, the design docs say you get the same kind of buffer back from substr on a buf, but we have subbuf for that now.

[lizmat]

Removing the tests and closing the ticket.