Re^2: map problem

I also found that adding a string cat operation seemed to clarify things enough for the parser also. I'm not sure which of the various solutions is "the best" if there even is such a thing!

#!/usr/bin/perl -w
use strict;
use Data::Dumper;

my %x = map {;   "prefix_$_" => 1 }    qw(a b c);
my %y = map {    "prefix_"."$_" => 1 } qw(a b c);
my %z = map { ''."prefix_$_" => 1 }    qw(a b c);
print Dumper \%y, \%x, \%z;
[download]

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Re^3: map problem by talexb (Chancellor) on Mar 09, 2012 at 17:44 UTC
I like a modification of your middle suggestion best: `my %y = map { "prefix_".$_ => 1 } qw(a b c);` [download] There's no need to put `$_` inside quotes, only to have Perl do variable interpolation on that string. :) Alex / talexb / Toronto "Groklaw is the open-source mentality applied to legal research" ~ Linus Torvalds	[reply] [d/l] [select]
Re^4: map problem by Marshall (Canon) on Mar 09, 2012 at 18:17 UTC
That will work just fine and dandy as near as I can tell. GREAT! - understandable! (in terms of what it does). For something like this I would probably add a comment in the code for others as tip to why this "understandable thing" was needed. Not just for the future readers, but you may even forget "why" after a few years. That stuff has happened to me before! If the technique is so tricky that you had to think a lot about it, put in a comment. But, yes, `"prefix_".$_ => 1` is "easy on the eyes" (and the brain)	[reply] [d/l]
Re^3: map problem by moritz (Cardinal) on Mar 09, 2012 at 21:00 UTC
I like the variant with the semicolon best, because it's the most explicit way to say that something should be parsed as a block. Which conveys a clear message to the maintenance programmer: I wanted a block here, and you'd better leave the semicolon there. Relying on the exact semantics of the disambiguation heuristics doesn't leave any traces in the code that there was a problem, and the unsuspecting maintenance programmer will run into the same problems as you did. Perl 6 - second systems done right	[reply]
Re^4: map problem by Marshall (Canon) on Mar 09, 2012 at 21:46 UTC
moritz you are completely right as a "black-belt" language syntax guy. You like the ";" first solution because it fits your thought model of "how it works" - it is "obvious" to you as a expert - but what may be obvious to you may not be obvious to others.	[reply]


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