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Re^2: $1 not "freezing" in an addition

by tobyink (Abbot)
on Dec 14, 2012 at 15:08 UTC ( #1008855=note: print w/replies, xml ) Need Help??

in reply to Re: $1 not "freezing" in an addition
in thread $1 not "freezing" in an addition

Here's another fun example...

use 5.010; my $z = 0; sub xxx () { $z = 1; return 2; } sub yyy () { my $zz = $z; $z = 0; return 2 + $zz; } if (xxx + yyy == yyy + xxx) { say "Addition is commutative"; } else { say "The world has gone haywire!"; }

See addition; commutativity; etc.

Don't write functions with side-effects. And if you really must write functions with side-effects, be careful using them in expressions.

perl -E'sub Monkey::do{say$_,for@_,do{($monkey=[caller(0)]->[3])=~s{::}{ }and$monkey}}"Monkey say"->Monkey::do'

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[Corion]: Meh. Once again I find that SQLite doesn't support window functions and I want to use those nowadays :-)
[erix]: Look what I found! :P
[Corion]: Hmm - actually, I don't need them, even though they'd be nice. I just want the (say) 10 latest images, and that's easily done with a limit 10 offset 0 clause, as I don't need all top 10 images for all users.
[Corion]: erix: Sure, but this is for a really-lightweight application and I'm replacing a CSV file / JSON file for user configuration with SQLite (and optionally, Pg) :)
[erix]: isn't a texty format handier for configs?
[Corion]: So far, I've avoided having even a user database by storing the user information in a (signed) cookie that the browser keeps for me, but as I want to be able to lock users, I need a second storage option :)
[Corion]: erix: It's needed for keeping the list of users and the list of tags associated with an image, and for keeping the images with users. I want an easy way to know if an image can be deleted, which means that it can't be referenced by any tag anymore. ...
[Corion]: SQL feels like a natural choice here :)

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