Re: remove duplicate values from array
On Apr 22, Jon Howe said: Can anyone tell me the best method for removing duplicate array values. I think the FAQ answers this best. perldoc -q uniq -- Jeff japhy Pinyan [EMAIL PROTECTED] http://www.pobox.com/~japhy/ RPI Acacia brother #734 http://www.perlmonks.org/ http://www.cpan.org/ ** Look for Regular Expressions in Perl published by Manning, in 2002 ** stu what does y/// stand for? tenderpuss why, yansliterate of course. [ I'm looking for programming work. If you like my work, let me know. ] -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
RE: remove duplicate values from array
Can anyone tell me the best method for removing duplicate
array values.
eg:
@array = qw( a a a b b b c);
becomes after some operation I cant seem to figure:
@new_array_or_same = (a b c);
In this situation, I usually use a hash instead of an array so I can
create highly useful statistics of how often each value occurs.
So I would do:
$hash{a}++ or $hash{b}++ or $hash{c}++
And then, like Jeff said, you could look in the manpage and get your
array from this hash you've created using the keys function like so:
@array = keys %hash;
Cheers,
-dave
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Re: remove duplicate values from array
i`m not quite shure because i`m a newbie to, but try using some RegExp like tr/some pattern/final idea/ and dont forget that tr// and s// have many more functions ex. using the (?). The book that i find most explainable about RegExp is Beginning Perl from Wrox Publishing. - Cheers, Miroslav Nikolov - On Mon, 22 Apr 2002, Jon Howe wrote: Can anyone tell me the best method for removing duplicate array values. eg: @array = qw( a a a b b b c); becomes after some operation I cant seem to figure: @new_array_or_same = (a b c); -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
Re: remove duplicate values from array
On Monday, April 22, 2002, at 09:29 , David Gray wrote:
Can anyone tell me the best method for removing duplicate
array values.
eg:
@array = qw( a a a b b b c);
becomes after some operation I cant seem to figure:
@new_array_or_same = (a b c);
In this situation, I usually use a hash instead of an array so I can
create highly useful statistics of how often each value occurs.
good reason to not use an autonomous hash.
what I just learned would solve the problem would be
my @array = qw( a a a b b b c);
my @new_array = keys %{{ map { $_ = 1 } @array}};
since the perldoc -q uniq that jeff provided pokes in
that direction - but was 'hash' oriented.
and, ok, so I am working out the questions:
So why Exactly do I want to have 'map' to begin with?
given perldoc -f map
ciao
drieux
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Re: remove duplicate values from array
From: drieux [EMAIL PROTECTED]
On Monday, April 22, 2002, at 09:29 , David Gray wrote:
Can anyone tell me the best method for removing duplicate
array values.
eg:
@array = qw( a a a b b b c);
becomes after some operation I cant seem to figure:
@new_array_or_same = (a b c);
In this situation, I usually use a hash instead of an array so I can
create highly useful statistics of how often each value occurs.
good reason to not use an autonomous hash.
what I just learned would solve the problem would be
my @array = qw( a a a b b b c);
my @new_array = keys %{{ map { $_ = 1 } @array}};
since the perldoc -q uniq that jeff provided pokes in
that direction - but was 'hash' oriented.
Yes you can do that. But it's slow ...
my @array = qw( a a a b b b c);
my @new_array;
{ my %h; @h{@array} = (); @new_array = keys %h; }
using a named lexical hash and hash slice instead of map is
quicker:
Benchmark: timing 2 iterations of Faq, Mine...
Faq: 10 wallclock secs ( 9.62 usr + 0.00 sys = 9.62 CPU)
@ 2078.35/s (n=2)
Mine: 1 wallclock secs ( 1.57 usr + 0.00 sys = 1.57 CPU)
@ 12722.65/s (n=2)
#!perl
use Benchmark;
@array = ((qw( a a a b b b c d d d f f u u u u u i i a y s e t x)) x 10);
sub Mine {
my @new_array;
{ my %h; @h{@array} = (); @new_array = keys %h; }
return scalar(@new_array);
}
sub Faq {
my @new_array = keys %{{ map { $_ = 1 } @array}};
return scalar(@new_array);
}
timethese 2, {
Mine = \Mine,
Faq = \Faq,
};
__END__
and, ok, so I am working out the questions:
So why Exactly do I want to have 'map' to begin with?
map { $_ = 1 } @array
creates a list in form:
( $array[0] = 1, $array[1] = 1, $array[2] = 1, ...)
If you then create a hash out of this list, the $array[x] items
become keys and the 1s become values.
So
1. map { $_ = 1 } @array
creates list of keys and values
2. {map { $_ = 1 } @array}
creates a reference to an anonymous hash
3. %{{map { $_ = 1 } @array}}
dereferences the reference
4. keys %{{map { $_ = 1 } @array}}
returns a list of keys.
Jenda
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Re: remove duplicate values from array
Hé ! Jenda
this slice thing is really very nice.
hash{@array1}=array2;
I saw it many times used in constructor of Object Oriented Perl's code.
Could you explain sequencely the syntax please ?
José.
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RE: remove duplicate values from array
Gosh.. what ever happened to good ol' grep
my %seen;
@uniq = grep !$seen{$_}++, @array;
-Original Message-
From: Jon Howe [mailto:[EMAIL PROTECTED]]
Sent: Monday, April 22, 2002 12:30 PM
To: [EMAIL PROTECTED]
Subject: remove duplicate values from array
Can anyone tell me the best method for removing duplicate
array values.
eg:
@array = qw( a a a b b b c);
becomes after some operation I cant seem to figure:
@new_array_or_same = (a b c);
The views and opinions expressed in this email message are the sender's
own, and do not necessarily represent the views and opinions of Summit
Systems Inc.
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Re: remove duplicate values from array
From: Jos Nyimi [EMAIL PROTECTED]
this slice thing is really very nice.
@hash{@array1}=@array2;
I saw it many times used in constructor of Object Oriented Perl's
code.
Could you explain sequencely the syntax please ?
Well I don't think I can make up a better explanation than the one
found in
perldoc perldata
in section Slices.
Jenda
P.S.: Nikola? The grep is slower than the slice:
Benchmark: timing 2 iterations of Faq, Mine, Nikola...
Faq: 10 wallclock secs ( 9.70 usr + 0.00 sys = 9.70 CPU)
@ 2061.01/s (n=2)
Mine: 1 wallclock secs ( 1.58 usr + 0.00 sys = 1.58 CPU)
@ 12642.23/s (n=2)
Nikola: 5 wallclock secs ( 4.40 usr + 0.00 sys = 4.40 CPU)
@ 4549.59/s (n=2)
=== [EMAIL PROTECTED] == http://Jenda.Krynicky.cz ==
There is a reason for living. There must be. I've seen it somewhere.
It's just that in the mess on my table ... and in my brain
I can't find it.
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Re: remove duplicate values from array
Ok, thanks !
I read it and every thing becomes clear to me :-)
José.
Jenda Krynicky [EMAIL PROTECTED] a écrit : From: José Nyimi
this slice thing is really very nice.
@hash{@array1}=@array2;
I saw it many times used in constructor of Object Oriented Perl's
code.
Could you explain sequencely the syntax please ?
Well I don't think I can make up a better explanation than the one
found in
perldoc perldata
in section Slices.
Jenda
P.S.: Nikola? The grep is slower than the slice:
Benchmark: timing 2 iterations of Faq, Mine, Nikola...
Faq: 10 wallclock secs ( 9.70 usr + 0.00 sys = 9.70 CPU)
@ 2061.01/s (n=2)
Mine: 1 wallclock secs ( 1.58 usr + 0.00 sys = 1.58 CPU)
@ 12642.23/s (n=2)
Nikola: 5 wallclock secs ( 4.40 usr + 0.00 sys = 4.40 CPU)
@ 4549.59/s (n=2)
=== [EMAIL PROTECTED] == http://Jenda.Krynicky.cz ==
There is a reason for living. There must be. I've seen it somewhere.
It's just that in the mess on my table ... and in my brain
I can't find it.
--- me
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Re: remove duplicate values from array
Assuming that the array has been converted to a scalar, then the following Lookaround Assertion works: #!/usr/bin/perl $_ = 'a a a b b c c'; 1 while s/\b(\w+) \s (?= \1\b ) //gxi; print $_, \n; The scalar can be reconverted to an array. Not sure if this is any faster. Alfred, Project Breeze SNPS -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
Re: remove duplicate values from array
On Monday, April 22, 2002, at 03:43 , Alfred Vahau wrote: Assuming that the array has been converted to a scalar, then the following Lookaround Assertion works: #!/usr/bin/perl $_ = 'a a a b b c c'; 1 while s/\b(\w+) \s (?= \1\b ) //gxi; print $_, \n; Survey Says: Benchmark: timing 2 iterations of Boink, Faq, Mine... Boink: 19 wallclock secs (18.58 usr + 0.00 sys = 18.58 CPU) @ 1076.43/s (n=2) Faq: 33 wallclock secs (31.72 usr + 0.00 sys = 31.72 CPU) @ 630.52/ s (n=2) Mine: 3 wallclock secs ( 3.74 usr + 0.00 sys = 3.74 CPU) @ 5347.59/s (n=2) upgrading jenda's original benchmark test so that we do not return the scalar in his, but do buy the conversion from an array to a scalar. assuming that it was in the scalar context the benchmark is: Benchmark: timing 2 iterations of Boink, Faq, Mine... Boink: 17 wallclock secs (15.70 usr + 0.00 sys = 15.70 CPU) @ 1273.89/s (n=2) ciao drieux --- -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
Re: remove duplicate values from array
On Monday, April 22, 2002, at 11:53 , Nikola Janceski wrote:
Gosh.. what ever happened to good ol' grep
my %seen;
@uniq = grep !$seen{$_}++, @array;
http://www.wetware.com/drieux/CS/lang/Perl/Beginners/BenchMarks/
will show you that this works just slightly slower than just
the hashing function
But clearly way better than everything but jenda's cool piece.
ciao
drieux
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