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Re^3: ~~ and list literal

by Anonymous Monk
on Oct 26, 2012 at 03:16 UTC ( #1000986=note: print w/replies, xml ) Need Help??

in reply to Re^2: ~~ and list literal
in thread ~~ and list literal


Because of precedence/binding


$ perl -le " $f = 1,2,3 ; print $f" 1 $ perl -MO=Deparse -le " $f = 1,2,3 ; print $f" BEGIN { $/ = "\n"; $\ = "\n"; } $f = 1, '???', '???'; print $f; -e syntax OK

Compare it to

$ perl -le " $f = ( 1,2,3 ); print $f" 3 $ perl -MO=Deparse -le " $f = ( 1,2,3 ) ; print $f" BEGIN { $/ = "\n"; $\ = "\n"; } $f = ('???', '???', 3); print $f; -e syntax OK

Since smart is binary (like = in the above example), it works on two scalars, left-scalar operator right-scalar

If you have no parentheses, the first scalar is taken, the closest, because assignment operator (=) has higher precedence than comma opeartor (it binds tighter).

If you add parenthesis, then you have the fabled List in Scalar Context, then the comma operator return the last right item (rightest most)

See Tutorials: Precedence for Idiots

Since you're confused about precedence you're probably also confused about context, so see Tutorials: Context in Perl: Context tutorial, "List" Is a Four-Letter Word, Easy Reference for Contexts

Smart match is giving me a headache...

Stop using it :) worked for me :) Smart-match

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[GotToBTru]: late to the conversation .. but thanks, Corion, for the reminder about Perl::Tidy
[Corion]: GotToBTru: Heh ;) I'm not really endorsing it, as I found that any gains made through it are easily squandered by the hours spent on configuring it. At least in my case :)
[GotToBTru]: Like most Swiss Army Knives, you can cut yourself trying to find the blade you actually want
[GotToBTru]: i am satisfied with the default settings turning the seemingly random formatting into something reliable
[Corion]: GotToBTru: Yeah, I started a quick(ly implemented but slowly running) implementation of a program that would guess the "best" configuration (that is, least amount of changes) from my code, but then found that it stops parsing the source as soon as it ..

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