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Re: strange list operator
by choroba (Cardinal) on Oct 09, 2015 at 08:36 UTC
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That's because list assignment is not optimized.
- 4 long lists involved: @aa, @bb, 1 .. 2e7 twice, size 8e7;
- 3 lists involved, @aa, @bb, 1 .. 2e7, size 6e7;
- 2 lists involved, @cc, 1 .. 4e7, size 8e7;
- 1 list involved, size 4e7.
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But how explain example 5?
I am trying to improve my English skills, if you see a mistake please feel free to reply or /msg me a correction
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List assignment is not optimized, but for is.
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[d/l] |
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Re: strange list operator
by Tux (Canon) on Oct 09, 2015 at 08:51 UTC
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What perl version? I seem to remember that there has been an optimization where older perls created the range on stack before copying it to the array and newer perls set the values directly.
Enjoy, Have FUN! H.Merijn
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Summary of my perl5 (revision 5 version 12 subversion 4) configuration
+:
Platform:
osname=MSWin32, osvers=5.2, archname=MSWin32-x86-multi-thread
uname=''
config_args='undef'
hint=recommended, useposix=true, d_sigaction=undef
useithreads=define, usemultiplicity=define
useperlio=define, d_sfio=undef, uselargefiles=define, usesocks=und
+ef
use64bitint=undef, use64bitall=undef, uselongdouble=undef
usemymalloc=n, bincompat5005=undef
that means all list assignment will use the same stack?
I am trying to improve my English skills, if you see a mistake please feel free to reply or /msg me a correction
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[d/l] |
Re: strange list operator
by Discipulus (Canon) on Oct 09, 2015 at 08:35 UTC
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[d/l] |
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Thanks for your reply, I add example 5. looks it works well but also hit limit.
I am trying to improve my English skills, if you see a mistake please feel free to reply or /msg me a correction
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Re: [Resolved?] strange list operator (tied array)
by mr_ron (Deacon) on Oct 09, 2015 at 15:59 UTC
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There sort of is a way to "implement range operator in perl source". Perl has a feature called tying that lets you implement indexing on an array yourself and lets you return something like the index of the element as the value. I have included a bare bones implementation of an array whose values are a sequence below. The solution has virtually no memory limitation on the size of the sequence.
package Tie::SeqArray;
use strict;
use warnings;
use parent 'Tie::Array';
sub TIEARRAY {
my $self = shift;
my $class = ref($self) || $self;
my $sequence_size = shift || die "sequence size of at least one re
+quired";
return bless {seq_size => $sequence_size};
}
sub FETCH {
my $self = shift;
my $i = shift;
return $i >= 0 && $i < $self->{seq_size} ? $i +1 : undef;
}
sub FETCHSIZE {
my $self = shift;
return $self->{seq_size};
}
package main;
use strict;
use warnings;
# from Perl Cookbook http://docstore.mik.ua/orelly/perl/cookbook/ch02_
+18.htm
sub commify {
my $text = reverse $_[0];
$text =~ s/(\d\d\d)(?=\d)(?!\d*\.)/$1_/g;
return scalar reverse $text;
}
my (@aa, @bb);
tie @aa, 'Tie::SeqArray', 20_000_000;
tie @bb, 'Tie::SeqArray', 20_000_000;
print $aa[100], ' ', commify(scalar(@aa)), "\n";
print commify($bb[19_999_001]), ' ', commify(scalar(@bb)), "\n";
__END__
101 20_000_000
19_999_002 20_000_000
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[d/l] |
Re: strange list operator
by Anonymous Monk on Oct 09, 2015 at 08:40 UTC
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Could anyone tell me how implement range operator in perl source? What?
I can't figure out how example 1 and 4 is broken.
How much ram do you have?
If 1..10_000_000 takes about 500mb, 4 times as much is going to take about 2GB ... which is about the limit for some systems
Running out of ram doesn't mean they're broken
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