Re^3: Array/List Strangeness (why)

Talking about bull ;-)

BTW, if you want to avoid this particular bit of magic, you can rewrite your list slice as an array slice: [get_a_list()]->[7,0]. And, as quietly noted in the documentation, if you want this behavior for an array slice, just write it as a list slice: (@array)[7,0].

I am pretty sure that slicing while dereferencing with right-arrow isn't (yet) implemented in perl!

  DB<71> x [qw/a b c/]->[2]                # works like expected
0  'c'
  DB<72> x [qw/a b c/]->[1,0]              # oops!
0  'a'
  DB<73> x [qw/a b c/]->[0,1]
0  'b'
[download]

Seems that instead to try slicing, the comma is interpreted in scalar context. Hence the last element of the slice-list is chosen as index!

UPDATE: the only way I know to slice lists like arrays is:

  DB<83> x @{[ qw// ]}[0,1]
0  undef
1  undef
  DB<84> x @{[ qw/a b c/ ]}[0,1]
0  'a'
1  'b'
[download]

Cheers Rolf

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Re^4: Array/List Strangeness (why) by tye (Sage) on Aug 05, 2009 at 18:14 UTC
Sorry, multi-value slices require more complex syntax: `@{[1,2,3]}[8,1,9]`. The `->` only works when you just want one value back. The `@{ }` form isn't actually much more verbose, but it is rather uglier. There was a patch to allow `[...]->@[...]` syntax (and I believe there is even a fork of Perl5 that includes such a patch) but it never got applied to official Perl 5 (I don't think I ever saw a good reason given for why it shouldn't be applied, though). - tye	[reply] [d/l] [select]
Re^5: Array/List Strangeness (why) by LanX (Saint) on Aug 05, 2009 at 18:29 UTC
multi-value slices require more complex syntax which is really a pity since it breaks the "always dereference with arrow" rule in PBP. I don't think I ever saw a good reason given for why it shouldn't be applied, though "Mythical" backwards compability? ;-) Personally i'd like to have a pragma like `strict` that bans the "scalar comma operator" ... I have much more trouble than fun with it ... 8( Cheers Rolf	[reply] [d/l]


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