Re: Mini-Tutorial: Working with Odd/Even Elements

by moritz (Cardinal)

on Jul 09, 2009 at 18:45 UTC ( #778656=note: print w/replies, xml )

Need Help??

my $t = 1;
grep { $t^=1 } LIST
[download]

If you're on perl-5.10 or newer, you can also use a state variable inside the block, and thus not "tainting" the outer scope:

use 5.010;

say grep { state $t = 1; $t ^= 1} <a b c d>;

# prints: bd
[download]

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Re^2: Mini-Tutorial: Working with Odd/Even Elements by ikegami (Patriarch) on Jul 09, 2009 at 19:22 UTC
That's not very useful outside of one-liners since it'll remember the state from the previous loop pass or function call.	[reply]
Re^2: Mini-Tutorial: Working with Odd/Even Elements by JavaFan (Canon) on Jul 09, 2009 at 19:02 UTC
`$ perl -wE 'say grep {state $t ^= 1} qw[a b c d]' ac $` [download]	[reply] [d/l]
Re^3: Mini-Tutorial: Working with Odd/Even Elements by salva (Canon) on Jul 09, 2009 at 19:14 UTC
oops... `$ perl -de 1 ... DB<1> use 5.010; sub a { grep { state $t ^= 1 } @_ } DB<2> x a(1..5) 0 1 1 3 2 5 DB<3> x a(1..5) 0 2 1 4` [download]	[reply] [d/l]
Re^4: Mini-Tutorial: Working with Odd/Even Elements by JavaFan (Canon) on Jul 09, 2009 at 19:33 UTC
That's a feature! You first get the odd elements, then the evens! ;-) ;-)	[reply]

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