in reply to grep items not matching an RE

Replace the NOT with a ! 
my @goodList = grep !/$bad/, @list;

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Re: Re: grep items not matching an RE
by bangers (Pilgrim) on May 14, 2004 at 11:31 UTC
    doh :-*

    Sorry I tried: 

    my @goodList = grep not /$bad/, @list;

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    I assumed that ! and NOT were the same. Does this work because ! has a different opperator precedence?
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[d/l]
      Does this work because ! has a different opperator precedence?
      Yes, 
      grep not /$bad/, @list;

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      is parsed as 
      grep not(/$bad/, @list);

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      since not has lower precedence than ,
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Re: Re: grep items not matching an RE
by muba (Priest) on May 14, 2004 at 11:32 UTC
    Hey, cool

    I always did that with my @goodList = grep {$_ !~ /$bad/} @list but your way looks a lot better, without the $_ thingy.
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[d/l]

      The EXPR version's also a good bit faster since it doesn't have to do the block enter/leave setup each item. 

      $ perl -MBenchmark=cmpthese -le 'cmpthese( 500_000, { BLOCK => sub { g
+rep { /a/ } qw( aa bb ab cd ef ) }, EXPR => sub { grep /a/, qw( aa bb
+ ab cd ef ) }, } )'
Benchmark: 
timing 500000 iterations of
 BLOCK, EXPR
...

     BLOCK: 16 wallclock secs (16.78 usr +  0.05 sys = 16.83 CPU) @ 29
+712.16/s (n=500000)

      EXPR:  4 wallclock secs ( 3.90 usr +  0.04 sys =  3.94 CPU) @ 12
+6984.13/s (n=500000)

          Rate BLOCK  EXPR
BLOCK  29712/s    --  -77%
EXPR  126984/s  327%    --

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