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Re: popping, shifting or splicing an array???

by injunjoel (Priest)
on Aug 09, 2005 at 18:50 UTC ( #482368=note: print w/replies, xml ) Need Help??


in reply to popping, shifting or splicing an array???

Greetings all,
Sounds like a job for grep to me.
Going with the
as numbers are selected remove elements from array A repopulate list with what is remaining into array A print array A
#!/usr/bin/perl -w use strict; use Dumpvalue; my $d = new Dumpvalue; #testing my @ArrayA = (0 .. 100); print "before\n"; $d->dumpValues(\@ArrayA); print "\n"; #more testing. my @numbers_to_remove = (14 .. 36, 50 .. 63, 89, 91, 94); #here we reassign @ArrayA with the return value from #our do{} block. @ArrayA = do { #make a local copy of @ArrayA as is to begin with my @tmp = @ArrayA; #map returns a list which comes in handy here map{ #make a local copy of the incoming elements from #our local copy in @tmp my $key = $_; #use a ternary operator to make sure we are #not including numbers from our #@numbers_to_remove list. If it is not #found return it otherwise return an #empty list. (!grep /^$key$/, @numbers_to_remove) ? $key : (); }@tmp; #for each element in @tmp }; print "After\n"; $d->dumpValues(\@ArrayA); print "\n";

Seems to work fine for me but I have not benchmarked this code.
Is this what you are looking for?

After re-reading the post I would suggest going with an Array of hashes depending on what is contained in the elements of @ArrayA. Hypothetically lets say you have a hash on information returned from a database query and you store a reference to each hash in the array @ArrayB. Then let the user select which elements to remove from the array based on some id.
use Dumpvalue; my $d = new Dumpvalue; #create the hypothetical structure. An array of #hash references each with an id field in it. my @ArrayB = map{{id=>$_}}(0 .. 100); $d->dumpValues(\@ArrayB); print "\n"; #more testing. #these would correspond to id's to remove in our hypothetical #scenario. my @ids_to_remove = (14 .. 36, 50 .. 63, 89, 91, 94); @ArrayB = do{ my @tmp = @ArrayB; map{ my $key = $_->{id}; (!grep /^$key$/, @ids_to_remove) ? $_ : () ; }@tmp; }; $d->dumpValues(\@ArrayB); exit;

Update!
I added some comments to the first block of code to hopefully explain what is going on.


-InjunJoel
"I do not feel obliged to believe that the same God who endowed us with sense, reason and intellect has intended us to forego their use." -Galileo

Replies are listed 'Best First'.
Re^2: popping, shifting or splicing an array???
by drock (Beadle) on Aug 09, 2005 at 19:01 UTC
    InjunJoel, looks good, but will you explain this in english. I read from bottom up correct?
Re^2: popping, shifting or splicing an array???
by drock (Beadle) on Aug 10, 2005 at 21:00 UTC
    Joel, I have to disagree. An array of hashes is really not necessary b/c I do not need to lookup or reference any element by name. What is in the elements is H02043-H02999 for example. All I need is once the user selection is stored in my tape_import array I need to splice these selections out of the main array and present an updated main array or a whole new array. Here is my code thus far:
    sub import99 { print $q->h3 ({-style=>'Color:#0000CC'},'Please Choose 9940 Tape Ran +ge for Import.'), $q->h3 ({-style=>'Color:#CC3300'},'Note: Inject Tapes via Acsls Prior +To Import!'); my @H99tapes =('H02043' .. 'H02999'); ##--##MAINARRAY my @UserH99tapes = @H99tapes;##--## USER SELECTIONS print $q->scrolling_list('htapes99',[@H99tapes],[$H99tapes[0]],10,-mul +tiple=>'true',my %attributes), $q->submit('form','Submit'), $q->reset; ##--BEGINIMPORT ##--## AS H NUMBERS ARE SELECTED, REMOVE SUBMITTED ELEMENTS ##--## FRO +M USER ARRAY ##--## REPOPULATE LIST INTO NEW ARRAY,PRINT NEW ARRAY my @tape_imports = $q->param(htapes99); ##--## SELECTED BY USER my $tape_count = scalar @tape_imports; $[=0; foreach (@tape_imports) { splice (@H99tapes,0,$tape_count,@H99tapes) } } ##--## END ROUTINE import99 ##--##
      Greetings again,
      Okay so maybe the hash in not in order but I have a few questions about your current approach.
      Since you are allowing for multiple selections in your scrolling_list
      print $q->scrolling_list('htapes99',[@H99tapes],[$H99tapes[0]],10,-mul +tiple=>'true',my %attributes);
      if the user selected four elements from random places in the list then the first five values are clipped from the list, four times. Not the elements the user selected.
      my $tape_count = scalar @tape_imports; foreach (@tape_imports) { splice (@H99tapes,0,$tape_count,@H99tapes) }
      It seems like each time through your foreach (hypothetically four times) you clip the the elements in @H99tapes from 0 to $tape_count (in this case 4) so five elements are removed from the beginning of the array. Also by replacing the missing values with the entire list again you are increasing the size of your list almost exponentially, at least by a factor of scalar(@H99tapes) - (scalar(@tape_imports) + 1). In a test I ran with your code and four random values the resulting size of @H99tapes was 15252! Its starting size was 957.
      The impetus behind my hash suggestion was that you could use the map to remove those elements with the same value as those the user selected rather than trying to manipulate the list based on positional index, however looking at your code a hash is not in order, yet the logic still is. So it seems like you would want to remove those values stored in @tape_imports from the @H99tapes list. In that case you could use the first example from my previous post.
      my @H99tapes =('H02043' .. 'H02999'); #...form stuff here my @tape_imports = $q->param(htapes99); #clean out all the values in @tape_imports from @H99tapes @H99tapes = do{ my @a = @H99tapes; #make a local copy of our list #now @a gets fed element by element into our map block #and its value is assigned to $_ map { #local copy of incoming value for map. We do this #because grep also assigns its values to $_ so #in order to not confuse things we assign it to a #locally scoped var $v my $v = $_; #check if this value is in the forbidden #list @tape_imports or not. We anchor the #regexp to avoid partial matches from other #values like '90' matching against '1905'. (!grep /^$v$/, @tape_imports) ? $v : (); } @a; };
      Does that makes sense? Or am I not getting it? I think splice might not be what you are looking for since it deals with postional indexing rather than element values. You would need to know what postions in your @H99tapes array the user selected elements are at in order to accurately splice them out. Since map returns a list we can just re-write the @H99tapes array with a grep call to filter out unwanted values, regardless of position.

      -InjunJoel
      "I do not feel obliged to believe that the same God who endowed us with sense, reason and intellect has intended us to forego their use." -Galileo

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