Re^2: Rosetta PGA-TRAM

Why does the block use $^a in one place (the automatic parameter) and $a in another place? Shouldn't that be a different (undeclared) variable? (Likewise for b).

If you move the uc you can avoid copying the whole string. Not much savings for a small string I suppose, but you break the clean pipeline nature by copying the input first, rather than doing nothing more than passing each character through the pipeline.

   $x.split('').map({ %rtoa{$_.uc} }).reduce: { $^a+$^b-$a%$b*2 }
[download]

Here's a shaken-up version, starting with noticing how the list return of a for loop is similar to the map function:

   sub infix:<ↀ> ($a,$b) { $a+$b-$a%$b*2 }
   [ↀ] do for $x.split('') { %rtoa{$_.uc} }

and an excuse to show off the cool form of the reduction metaoperator.

P.S.: used pre instead of code because Perl Monks still doesn't like Unicode. code escapes out the entities, and the form isn't submitted in UTF-8 so various things are automatically encoded. Nasty.

Comment on Re^2: Rosetta PGA-TRAM Download Code

Replies are listed 'Best First'.
Re^3: Rosetta PGA-TRAM by moritz (Cardinal) on Jun 17, 2009 at 22:42 UTC
Why does the block use $^a in one place (the automatic parameter) and $a in another place? Shouldn't that be a different (undeclared) variable? (Likewise for b). No, the `^` twigil is only necessary in the first occurrence. That was introduced because things like this: `my $block = { my $v = %hash{$^key}; say "The lookup {%hash{$^key}} yields $v"; };` [download] Would complain about the closure inside the string getting no argument, because `$^key` was interpreted as a formal parameter to the inner-most closure, which in this case was the one inside the string. Or more general, you couldn't refer to outer lexicals that happened to be self-declaring formal parameters. So it was decided that after `$^foo` occurred once, you could refer to it as `$foo` to, disambiguating it in inner blocks.	[reply] [d/l] [select]
Re^4: Rosetta PGA-TRAM by John M. Dlugosz (Monsignor) on Jun 17, 2009 at 22:56 UTC
I see. I must have overlooked that when I read through the diffs with the last version I studied carefully. It's so easy to overlook changed or especially removed things!	[reply]