Beefy Boxes and Bandwidth Generously Provided by pair Networks
go ahead... be a heretic
 
PerlMonks  

Comment on

( #3333=superdoc: print w/ replies, xml ) Need Help??
Like grep but returns the first match. successive calls return successive elements.
This was the solution to a reference problem I was working on awhile back. It was one of those things that I wanted to do, just to do it because it should be possible. (Have a sub that remembers some context info.)
Plus I like the construct :).
#!/usr/bin/perl ###################################################################### +############### # findone # usage: findone { coderef }, @array , OPTIONAL start_index OPTIONAL +end_index # Like grep but returns the first match. successive calls return succe +ssive elements. # Can be nested. Uses Weak references to prevent the leaking of memory +. ###################################################################### +############### BEGIN { use warnings; use strict; use WeakRef; my %find_cache = (); # Temporary Storeage. sub findone(&\@;$$) { my $coderef = shift ; # Generate a key from the caller function so we can track whic +h call it is. my $codekey = join(":",caller(),"$_[0]"); # Generate key my %persistant_args = () ; ############################################################## +########## # Clean up old keys to prevent leaking mem. If the data does +not exist, # then it has been freed and we don't need to keep position in +fo. ############################################################## +########## while(my ($k,$v) = each %find_cache){ delete $find_cache{$k} unless defined ($v->{dataref}); } unless (defined $find_cache{$codekey} ){ %persistant_args = ('index' =>($_[1]||0), 'dataref' => $_[ +0] ); }else{ %persistant_args = %{$find_cache{$codekey}}; } my $end_index = $_[2] || $#{ $_[0] }; for (; $persistant_args{index} <= $end_index; $persistant_ar +gs{index}++ ){ $_ = $_[0]->[$persistant_args{index}]; if (&$coderef){ $persistant_args{index}++; $find_cache{$codekey} = {%persistant_args}; weaken ($find_cache{$codekey}->{dataref}); return wantarray ? ($_ ,($persistant_args{index} -1 ) + ) : $_; } } delete $find_cache{$codekey}; return; } } ########################### # Silly Example # ########################### my @words = (qw(this Is a silly coNtrived Test)) x 5; print "\@words is $#words\n"; while ( my ( $val ,$index ) = findone { m/[A-Z]/ } @words ){ print "_" x 40,"\n"; print "Matched uppercase letter $val at $index \n"; while ( my ( $otherval ,$otherindex ) = findone { !m/[A-Z]/ } +@words , 10, 22 ){ print "\tInner matched all lower $otherval at $otherindex\n"; } sleep(1); }
updated Changes in response to jynx
updated Changed to accept end_index as well.
updated Changed to use stringified reference in cache key.
Now you can nest them.
my @AoA = (Array of arrays);

while ( my ($val,$index) = findone { findone{ other_criteria } @{$_} } @AoA ){

}
UPDATE: Subtle Bug/Feature, see this. I have a newer version that uses Filter::Simple, but I still hope to fix this without resorting to it.
UPDATE: Rough filter simple version here.

-Lee

"To be civilized is to deny one's nature."

In reply to findone { coderef } @array by shotgunefx

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post; it's "PerlMonks-approved HTML":



  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • Outside of code tags, you may need to use entities for some characters:
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.
  • Log In?
    Username:
    Password:

    What's my password?
    Create A New User
    Chatterbox?
    and the web crawler heard nothing...

    How do I use this? | Other CB clients
    Other Users?
    Others musing on the Monastery: (4)
    As of 2014-08-30 16:31 GMT
    Sections?
    Information?
    Find Nodes?
    Leftovers?
      Voting Booth?

      The best computer themed movie is:











      Results (293 votes), past polls