Anonymous Arrays or Anonymous Array References

Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

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Re: Anonymous Arrays or Anonymous Array References by kennethk (Abbot) on Mar 03, 2011 at 15:24 UTC
When you write `print (1,2,3)[1]`, the interpreter associates the parentheses with the function call, not with a list assignment. In that interpretation, the array index is a meaningless syntax error. To get the functionality you expect, you require `print( (1,2,3)[1] );` Your second case is equivalent to `print( [1,2,3]->[1] );`. This is all a consequence of letting parentheses be optional for built-ins, and is discussed a bit in perlsyn.	[reply] [d/l] [select]
Re: Anonymous Arrays or Anonymous Array References by Fletch (Bishop) on Mar 03, 2011 at 15:35 UTC
The first would work if you provided an extra set of parens or unary plus to make it parse the way you intended it to in light of the optional paren behavior. `$ perl -MO=Deparse,-q,-p -e 'print +(1,2,3)[1];' print(((1, 2, 3))[1]); -e syntax OK $ perl -MO=Deparse,-q,-p -e 'print( (1,2,3)[1] );' print(((1, 2, 3))[1]); -e syntax OK` [download] The cake is a lie. The cake is a lie. The cake is a lie.	[reply] [d/l]
Re: Anonymous Arrays or Anonymous Array References by Anonymous Monk on Mar 03, 2011 at 15:53 UTC
My eyes are opened! Then is there a way to coerce an array with parenthesis into a hash? `@U = keys ('A'=>1,'B'=>2,'Z'=>26);` [download] Mostly I have been using the following approach: `@U = keys %{{ map { $_=>1} @NU }};` [download]	[reply] [d/l] [select]
Re^2: Anonymous Arrays or Anonymous Array References by moritz (Cardinal) on Mar 03, 2011 at 16:26 UTC
Not with parenthesis, which create lists. The `%{ { ... } }` is the shortest way I know of. Perl 6 - second systems done right	[reply] [d/l]
Re^2: Anonymous Arrays or Anonymous Array References by ikegami (Patriarch) on Mar 03, 2011 at 19:07 UTC
`@U = keys ('A'=>1,'B'=>2,'Z'=>26);` That's the same as getting every second item (starting with the first) and removing duplicates. There's no good shorthand for that, even if you omit the requirement to remove duplicates. `@U = keys %{{ map { $_=>1} @NU }};` If the contents of @NU has no duplicates, then that's the same as `my @U = @NU;` [download] If your question is how to remove duplicates, then there's an answer in perlfaq4. Some solutions `my @U = uniq @NU; # From List::Util` [download] I use the idiomatic `my %seen; my @U = grep !$seen{$_}++, @NU;` [download]	[reply] [d/l] [select]