Array splitting

Hopfi has asked for the wisdom of the Perl Monks concerning the following question:

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Re: Array splitting by Kenosis (Priest) on Oct 31, 2012 at 21:42 UTC
You need to use `eq` not `==`,as the latter's used for numeric comparisons: `if(substr($_,0,1) eq 'A') { ...` [download] Output: `Ape added to A Arg added to A Beep added to trash! Circus added to trash! Ape, Arg Beep, Circus` [download] Another option is to use a regex to check the beginning character: `if(/^A/) { ...` [download] Also, consider doing the following for your `print` statements: `... print "$_ added to A\n"; ... print "$_ added to trash!\n";` [download]	[reply] [d/l] [select]
Re^2: Array splitting by bimleshsharma (Beadle) on Nov 01, 2012 at 08:05 UTC
here is quick solution. See if it is useful for you. `sub split_array { my @not_sorted = qw(Ape Arg Beep Circus); my @sorted = sort {$a cmp $b} @not_sorted; my @A = (); my @trash = (); map{$_ =~/^A.*/ ? push(@A,$_):push(@trash,$_)} @sorted; print "\n",@A,"\n"; print "\n",@trash,"\n"; }` [download]	[reply] [d/l]
Re: Array splitting by AnomalousMonk (Archbishop) on Oct 31, 2012 at 22:00 UTC
... it skips the if in the foreach loop. When I run your OPed code, I see that the `else` (false) clause of the conditional statement is skipped, not the `if` (true) clause, which is always executed. The reason is that you are using a numeric `==` comparison to test for string equality. You should use the `eq` operator (see Equality Operators in perlop). Numeric comparisons of strings that have no leading decimal digits are always equal because such strings always evaluate to zero in numeric context. `>perl -wMstrict -le "print 'A' == 'B'; " Argument "B" isn't numeric in numeric eq (==) at -e line 1. Argument "A" isn't numeric in numeric eq (==) at -e line 1. 1` [download] And BTW: using warnings would have alerted you to this problem, and using strict ain't a bad idea, either.	[reply] [d/l] [select]
Re: Array splitting by Perlbotics (Archbishop) on Oct 31, 2012 at 22:24 UTC
TIMTOWTDI: `use strict; use warnings; my @not_sorted = qw(Ape Arg Beep Circus); my @sorted = sort {$a cmp $b} @not_sorted; my @A = grep { /^A/ } @sorted; my @trash = grep { !/^A/ } @sorted; print join(', ', @A) , "\n"; print join(', ', @trash) , "\n";` [download] You can even include the `printf(...)` in the grep block, i.e. at the beginning since the result of the block should be determined by the filter expression. Have a look at split to split an array by position. From the title of your OP, I first thought you meant that...	[reply] [d/l] [select]
Re: Array splitting by johngg (Canon) on Oct 31, 2012 at 22:50 UTC
The `{ $a cmp $b }` comparison is the default behaviour for sort so doesn't have to be mentioned specifically if you don't wish. You can populate your `@A` and `@trash` arrays in one go by eliminating the intermediate `@sorted` array and pushing onto the appropriate array using a ternary (see Conditional Operator). `$ perl -Mstrict -Mwarnings -E' > my @notSorted = qw{ Beep Ape Circus Arg }; > my( @A, @trash ); > push @{ $_ =~ m{^A} ? \ @A : \ @trash }, $_ for sort @notSorted; > do { > local $" = q{, }; > say qq{@A}; > say qq{@trash}; > };' Ape, Arg Beep, Circus $` [download] I hope this is helpful. Cheers, JohnGG	[reply] [d/l] [select]
Re^2: Array splitting by Hopfi (Novice) on Nov 01, 2012 at 00:18 UTC
Alright. Thanks very much guys! Im more a C++ guy and not used to those different operations (like eq != ==).	[reply]
Re: Array splitting by tobyink (Canon) on Nov 01, 2012 at 10:13 UTC
`use strict; use List::AssignRef; use List::MoreUtils qw( part ); my @not_sorted = qw(Ape Arg Beep Circus); (deref my @trash, deref my @A) = part { !!/^A/ } sort @not_sorted; print "Got A: @A\n"; print "Got trash: @trash\n";` [download] `perl -E'sub Monkey::do{say$_,for@_,do{($monkey=[caller(0)]->[3])=~s{::}{ }and$monkey}}"Monkey say"->Monkey::do'`	[reply] [d/l]