Re: given/when one case prefixes another

This works in Strawberry 5.10.1.4, but I don't know how 'proper' it is; frankly, it looks a bit hinky to me.

>perl -wMstrict -lE
"for my $s qw(a b c d) {
   given ($s) {
     when ('a')    { say 'a';  continue;  }
     when ('b')    { say 'b';  continue;  }
     when (/[ab]/) { say ' after a or b'; }
     say 'neither a nor b';
     when ('d')    { say 'd';             }
     default       { say qq{other: '$_'}; }
     }
   }
"
a
 after a or b
b
 after a or b
neither a nor b
other: 'c'
neither a nor b
d
[download]

BTW: I couldn't get the goto approach to work: Perl experiences a 'panic: goto' attack.

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Re^2: given/when one case prefixes another by moritz (Cardinal) on Apr 26, 2011 at 09:03 UTC
It seems like perfectly fine code to me. I guess you are wondering if the code directly in "given" (without a "when" clause) is "proper". The answer is yes. That's one feature that distinguishes given/when from the switch statement in C. But do consider that such code could become hard to read if the whole given/when doesn't fit onto one or two screen pages anymore - you shouldn't be doing very much in the when clauses (calling functions or methods should be fine). Perl 6 - second systems done right	[reply]
Re^3: given/when one case prefixes another by AnomalousMonk (Archbishop) on Apr 26, 2011 at 15:46 UTC
I suppose I was uneasy about the possibility of the `when (/[ab]/) { ... }` tail clause 'getting lost', dependent as it is on a `continue` statement in other, possibly distant, clauses, and on the relative positions of those clauses (also a dependency of Neighbour's approach). Taking apl's suggestion, I am more comfortable with something like the following, which encapsulates the tail of each 'tailed' clause within the clause itself: `>perl -wMstrict -lE "for my $s qw(a b c d) { given ($s) { my $tail_a_and_b = sub { say qq{ after a or b, was '$_' } }; when ('a') { say 'a'; $tail_a_and_b->(); } when ('b') { say 'b'; $tail_a_and_b->(); } when ('d') { say 'd'; } default { say qq{other: '$_'}; } } } " a after a or b, was 'a' b after a or b, was 'b' other: 'c' d` [download]	[reply] [d/l] [select]