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Re^2: map syntax error -- weird

by hdb (Parson)
on Mar 22, 2013 at 10:38 UTC ( #1024915=note: print w/ replies, xml ) Need Help??


in reply to Re: map syntax error -- weird
in thread map syntax error -- weird

Why does this work? (same result as your proposals)

my %opt; my @vals = qw(title artist album); my @opts = map { "$_"."=s" => \$opt{$_} } @vals; print @opts;

UPDATE: Guess: Because there is some statement in there that needs to be executed rather than a static string only?


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Re^3: map syntax error -- weird
by BrowserUk (Pope) on Mar 22, 2013 at 10:54 UTC
    Guess: Because there is some statement in there that needs to be executed rather than a static string only?

    Indeed.


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Re^3: map syntax error -- weird
by LanX (Canon) on Mar 22, 2013 at 10:54 UTC
    > Why does this work? (same result as your proposals)

    There is no clear rule to distinguish between code-block and hash-ref!!!

    The parser uses DWIM heuristics to guess if it looks more like a hash-ref or not. (Furthermore "w/o look-ahead")

    So in complicated cases you need to give hints for what you mean.

    This ambiguity should be one reason why Perl6 switched from {} to <> to indicate hashes.

    > UPDATE: Guess: Because there is some statement in there that needs to be executed rather than a static string only?

    well it's a perfect hash-ref!

    DB<112> $hr={ "$_"."=s" => \$opt{$_} } => { "=s" => \undef }

    But I think the used heuristic must be quite simple, something like

      (bareword || variable) (comma || fatcomma) (expr)

    So "$_"."=s" is already to complex to fit this rule of thumb.

    Cheers Rolf

    ( addicted to the Perl Programming Language)

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