[9550] in Perl-Users-Digest
Perl-Users Digest, Issue: 3144 Volume: 8
daemon@ATHENA.MIT.EDU (Perl-Users Digest)
Mon Jul 13 17:07:26 1998
Date: Mon, 13 Jul 98 14:01:35 -0700
From: Perl-Users Digest <Perl-Users-Request@ruby.OCE.ORST.EDU>
To: Perl-Users@ruby.OCE.ORST.EDU (Perl-Users Digest)
Perl-Users Digest Mon, 13 Jul 1998 Volume: 8 Number: 3144
Today's topics:
Re: Quickie: the number of occurences of a character in (David A. Black)
Re: Quickie: the number of occurences of a character in (Andre L.)
Re: Quickie: the number of occurences of a character in (Larry Rosler)
Re: Quickie: the number of occurences of a character in (Sean McAfee)
Re: Quickie: the number of occurences of a character in <dgris@rand.dimensional.com>
Re: Quickie: the number of occurences of a character in (David A. Black)
Re: Quickie: the number of occurences of a character in <dfan@harmonixmusic.com>
Recommend me Perl! c960901@student.dtu.dk
Re: References to Anonymous subroutines (Greg Ward)
Re: RegExps: Check if string consists of EXACTLY 3 digi (Michael J Gebis)
Re: RegExps: Check if string consists of EXACTLY 3 digi (brian d foy)
Re: RegExps: Check if string consists of EXACTLY 3 digi (Larry Rosler)
Re: RegExps: Check if string consists of EXACTLY 3 digi (Bob Trieger)
Re: RegExps: Check if string consists of EXACTLY 3 digi (Tad McClellan)
Sorting a 2-d array <gavery@uu.net>
Re: Sorting a 2-d array (brian d foy)
Re: Threads in Perl? NEWBIE ? (Josh Kortbein)
Special: Digest Administrivia (Last modified: 12 Mar 98 (Perl-Users-Digest Admin)
----------------------------------------------------------------------
Date: Mon, 13 Jul 1998 15:16:57 EDT
From: dblack@saturn.superlink.net (David A. Black)
Subject: Re: Quickie: the number of occurences of a character in a string
Message-Id: <6odmf9$26f$1@earth.superlink.net>
Hello -
shapiroj@logica.com writes:
>I want to find the number of occurences of a given character ($char) in a
>particular string, ($text). I thought there would be some cool, quick method
>to do this using m//, but all I've been able to come up with is:
>$number_of_occur = scalar ( @temp = ($text =~ /$char/g));
>which is nice because it's one-line, but the @temp array is ick. (And -w
>doesn't like it either.) Any suggestions?
You could do:
$num = $text =~ s/$char/$char/g;
or
$num = $text =~ s/($char)/$1/g; # which would be more /i friendly, if
# that mattered
David Black
dblack@saturn.superlink.net
------------------------------
Date: Mon, 13 Jul 1998 15:29:01 -0500
From: alecler@cam.org (Andre L.)
Subject: Re: Quickie: the number of occurences of a character in a string
Message-Id: <alecler-1307981529010001@dialup-740.hip.cam.org>
In article <6odh9t$s2g$1@nnrp1.dejanews.com>, shapiroj@logica.com wrote:
> I want to find the number of occurences of a given character ($char) in a
> particular string, ($text). I thought there would be some cool, quick method
> to do this using m//, but all I've been able to come up with is:
>
> $number_of_occur = scalar ( @temp = ($text =~ /$char/g));
>
> which is nice because it's one-line, but the @temp array is ick. (And -w
> doesn't like it either.) Any suggestions?
$num = () = $text =~ /$char/g;
HTH,
A.L.
------------------------------
Date: Mon, 13 Jul 1998 12:49:55 -0700
From: lr@hpl.hp.com (Larry Rosler)
Subject: Re: Quickie: the number of occurences of a character in a string
Message-Id: <MPG.101404bca3e7f4a1989706@nntp.hpl.hp.com>
[This followup was posted to comp.lang.perl.misc and a copy was sent to
the cited author.]
In article <6odmf9$26f$1@earth.superlink.net> on Mon, 13 Jul 1998
15:16:57 EDT, David A. Black <dblack@saturn.superlink.net> says...
...
> You could do:
>
> $num = $text =~ s/$char/$char/g;
>
> or
>
> $num = $text =~ s/($char)/$1/g; # which would be more /i friendly, if
> # that mattered
What makes you think that? These two statements have identical
functions.
--
Larry Rosler
Hewlett-Packard Laboratories
http://www.hpl.hp.com/personal/Larry_Rosler/
lr@hpl.hp.com
------------------------------
Date: Mon, 13 Jul 1998 19:56:47 GMT
From: mcafee@breakout.rs.itd.umich.edu (Sean McAfee)
Subject: Re: Quickie: the number of occurences of a character in a string
Message-Id: <3Etq1.3598$24.20589724@news.itd.umich.edu>
In article <6odh9t$s2g$1@nnrp1.dejanews.com>, <shapiroj@logica.com> wrote:
>I want to find the number of occurences of a given character ($char) in a
>particular string, ($text). I thought there would be some cool, quick method
>to do this using m//, but all I've been able to come up with is:
>$number_of_occur = scalar ( @temp = ($text =~ /$char/g));
>which is nice because it's one-line, but the @temp array is ick. (And -w
>doesn't like it either.) Any suggestions?
$n = $i = 0; $n++ while ($i = index($text, $char, $i) + 1) > 0;
I benchmarked these two methods (as well as a third which was mentioned by
someone else), counting the number of e's in /usr/dict/words:
----------------------------------------------------------------------
use Benchmark;
open(DICT, "/usr/dict/words") ? ($a = join("", <DICT>)) : die;
close(DICT);
timethese(500, {
RegExp => sub { my ($n,@temp); $n = scalar (@temp = $a =~ /e/g); },
RegExp2 => sub { my $n = () = $a =~ /e/g; },
Index => sub { my ($i,$n)=(0,0); $n++ while ($i=index($a,"e",$i)+1) > 0 }
});
----------------------------------------------------------------------
Benchmark: timing 500 iterations of Index, RegExp, RegExp2...
Index: 111 secs (85.10 usr 0.00 sys = 85.10 cpu)
RegExp: 140 secs (119.48 usr 0.05 sys = 119.53 cpu)
RegExp2: 146 secs (83.29 usr 0.07 sys = 83.36 cpu)
--
Sean McAfee | GS d->-- s+++: a26 C++ US+++$ P+++ L++ E- W+ N++ |
| K w--- O? M V-- PS+ PE Y+ PGP?>++ t+() 5++ X+ R+ | mcafee@
| tv+ b++ DI++ D+ G e++>++++ h- r y+>++** | umich.edu
------------------------------
Date: Mon, 13 Jul 1998 20:35:28 GMT
From: Daniel Grisinger <dgris@rand.dimensional.com>
Subject: Re: Quickie: the number of occurences of a character in a string
Message-Id: <6odqck$k44$1@rand.dimensional.com>
[posted to comp.lang.perl.misc and mailed to the cited author]
In article <MPG.101404bca3e7f4a1989706@nntp.hpl.hp.com>
lr@hpl.hp.com (Larry Rosler) wrote:
>In article <6odmf9$26f$1@earth.superlink.net> on Mon, 13 Jul 1998
>15:16:57 EDT, David A. Black <dblack@saturn.superlink.net> says...
>> $num = $text =~ s/$char/$char/g;
>> $num = $text =~ s/($char)/$1/g; # which would be more /i friendly, if
>> # that mattered
>What makes you think that? These two statements have identical
>functions.
Yes, but if you add /i then the second version will preserve case.
$ perl -w
$a = $b = 'this is a test';
$char = 'T';
$a =~ s/$char/$char/ig;
$b =~ s/($char)/$1/ig;
print $a, "\n";
print $b, "\n";
__END__
This is a TesT
this is a test
$
Regards,
Daniel
--
Daniel Grisinger dgris@perrin.dimensional.com
"No kings, no presidents, just a rough consensus and
running code."
Dave Clark
------------------------------
Date: Mon, 13 Jul 1998 16:23:38 EDT
From: dblack@saturn.superlink.net (David A. Black)
Subject: Re: Quickie: the number of occurences of a character in a string
Message-Id: <6odqca$a6h$1@earth.superlink.net>
Hello -
lr@hpl.hp.com (Larry Rosler) writes:
>[This followup was posted to comp.lang.perl.misc and a copy was sent to
>the cited author.]
>In article <6odmf9$26f$1@earth.superlink.net> on Mon, 13 Jul 1998
>15:16:57 EDT, David A. Black <dblack@saturn.superlink.net> says...
>...
>> You could do:
>>
>> $num = $text =~ s/$char/$char/g;
>>
>> or
>>
>> $num = $text =~ s/($char)/$1/g; # which would be more /i friendly, if
>> # that mattered
>What makes you think that? These two statements have identical
>functions.
If one were to add the /i modifier to each of these,
the first would flatten case to the case of $char, whereas the
second would not; hence I described the second as more /i
friendly.
But see Andre's post anyway for a better solution not involving
substitution.
David Black
dblack@saturn.superlink.net
------------------------------
Date: 13 Jul 1998 16:39:50 -0400
From: Dan Schmidt <dfan@harmonixmusic.com>
Subject: Re: Quickie: the number of occurences of a character in a string
Message-Id: <wkoguth4dl.fsf@turangalila.harmonixmusic.com>
mcafee@breakout.rs.itd.umich.edu (Sean McAfee) writes:
| ----------------------------------------------------------------------
| use Benchmark;
|
| open(DICT, "/usr/dict/words") ? ($a = join("", <DICT>)) : die;
| close(DICT);
|
| timethese(500, {
| RegExp => sub { my ($n,@temp); $n = scalar (@temp = $a =~ /e/g); },
| RegExp2 => sub { my $n = () = $a =~ /e/g; },
| Index => sub { my ($i,$n)=(0,0); $n++ while ($i=index($a,"e",$i)+1) > 0 }
| });
| ----------------------------------------------------------------------
|
| Benchmark: timing 500 iterations of Index, RegExp, RegExp2...
| Index: 111 secs (85.10 usr 0.00 sys = 85.10 cpu)
| RegExp: 140 secs (119.48 usr 0.05 sys = 119.53 cpu)
| RegExp2: 146 secs (83.29 usr 0.07 sys = 83.36 cpu)
|
| --
You can do better than that:
timethese(500, {
RegExp => sub { my ($n,@temp); $n = scalar (@temp = $a =~ /e/g); },
RegExp2 => sub { my $n = () = $a =~ /e/g; },
Index => sub { my ($i,$n)=(0,0); $n++ while ($i=index($a,"e",$i)+1) > 0 },
Tr => sub { my $n = $a =~ tr/e/e/; }
});
--- results follow ---
Benchmark: timing 500 iterations of Index, RegExp, RegExp2, Tr...
Index: 15 secs (14.67 usr 0.00 sys = 14.67 cpu)
RegExp: 27 secs (27.33 usr 0.00 sys = 27.33 cpu)
RegExp2: 21 secs (21.61 usr 0.00 sys = 21.61 cpu)
Tr: 2 secs ( 1.73 usr 0.00 sys = 1.73 cpu)
But that wasn't the original question anyway. In the original
question, the letter to search for wasn't determined until run-time.
--
Dan Schmidt -> dfan@harmonixmusic.com, dfan@alum.mit.edu
Honest Bob & the http://www2.thecia.net/users/dfan/
Factory-to-Dealer Incentives -> http://www2.thecia.net/users/dfan/hbob/
Gamelan Galak Tika -> http://web.mit.edu/galak-tika/www/
------------------------------
Date: Mon, 13 Jul 1998 19:39:02 GMT
From: c960901@student.dtu.dk
Subject: Recommend me Perl!
Message-Id: <6odnon$cul$1@nnrp1.dejanews.com>
Hello there.
I've never written a line of Perl, but I'm going to in the very near future.
I need someone to recommend me -the best- Perl book available. What can Perl
do? I've seen only little Perl code. Can it scan a directory for subdirs and
files and return the names in a string array? Cause that's what I really
need.
Thanks
Morten
-----== Posted via Deja News, The Leader in Internet Discussion ==-----
http://www.dejanews.com/rg_mkgrp.xp Create Your Own Free Member Forum
------------------------------
Date: 13 Jul 1998 18:54:52 GMT
From: greg@bic.mni.mcgill.ca (Greg Ward)
Subject: Re: References to Anonymous subroutines
Message-Id: <6odl5s$ob2@sifon.cc.mcgill.ca>
: $rs = sub {
: print "hello \n";
: };
:
: It's suppose to return a reference to the newly created sub. Can anyone tell
: me how it works?? Let say you declare such a routine can it be referenced to
: somewhere else in the program? And what would be the use in declaring an
: anonymous sub (Real world application).
I can't tell you in detail how this works, except that it does work
nicely. Some real-world applications:
* callbacks in GUI programs
* sub x needs to pass a bit of code to sub y, and wants to
do so without interfering with the symbol table (named subroutines
are always global in Perl)
* closures (anonymous subroutine that remembers the environment in
which it was created on subsequent invocations -- a bit spooky, but
very cool, and very useful for GUI programming)
Keep reading that fine book *Advanced Perl Programming* for more
information.
Greg
--
Greg Ward - Programmer/Analyst greg@bic.mni.mcgill.ca
Brain Imaging Centre (WB201) http://www.bic.mni.mcgill.ca/~greg
Montreal Neurological Institute voice: (514) 398-4965 (or 1996)
Montreal, Quebec, Canada H3A 2B4 fax: (514) 398-8948
------------------------------
Date: 13 Jul 1998 19:52:30 GMT
From: gebis@albrecht.ecn.purdue.edu (Michael J Gebis)
Subject: Re: RegExps: Check if string consists of EXACTLY 3 digits ??
Message-Id: <6odohu$d1u@mozo.cc.purdue.edu>
Karsten <karsten.no.123.spam@alpha.futurenet.co.za> writes:
}I am writing a CGI script which accepts input via QUERY_STRING.
}However, the input is only valid if it consists of EXACTLY 3 DIGITS! No
}more , no less, no other characters in front, after or in between the
}digits. Ive tried things such as:
#Untested but if I screw this up I deserve what I get.
if($string =~ m/^\d\d\d$/) { print "Valid\n"; }
--
Mike Gebis gebis@ecn.purdue.edu mgebis@eternal.net
------------------------------
Date: Mon, 13 Jul 1998 16:07:48 -0400
From: comdog@computerdog.com (brian d foy)
Subject: Re: RegExps: Check if string consists of EXACTLY 3 digits ??
Message-Id: <comdog-ya02408000R1307981607480001@news.panix.com>
Keywords: from just another new york perl hacker
In article <35AACA77.D9C@alpha.futurenet.co.za>, karsten.no.123.spam@alpha.futurenet.co.za posted:
>I am writing a CGI script which accepts input via QUERY_STRING.
>However, the input is only valid if it consists of EXACTLY 3 DIGITS! No
>more , no less, no other characters in front, after or in between the
>digits. Ive tried things such as:
>
>if ($ENV{'QUERY_STRING'} =~ /[0-9]\{3\}/)
why are you escaping the curlies? :)
try
$string =~ m/^\d{3}(?!\n)$/
--
brian d foy <comdog@computerdog.com>
CGI Meta FAQ <URL:http://computerdog.com/CGI_MetaFAQ.html>
Comprehensive Perl Archive Network (CPAN) <URL:http://www.perl.com>
Perl Mongers Travel Deals! <URL:http://www.pm.org/travel.html>
------------------------------
Date: Mon, 13 Jul 1998 13:00:27 -0700
From: lr@hpl.hp.com (Larry Rosler)
Subject: Re: RegExps: Check if string consists of EXACTLY 3 digits ??
Message-Id: <MPG.10140736fd810aed989707@nntp.hpl.hp.com>
[This followup was posted to comp.lang.perl.misc and a copy was sent to
the cited author.]
In article <35AACA77.D9C@alpha.futurenet.co.za> on Mon, 13 Jul 1998
20:03:19 -0700, Karsten <karsten.no.123.spam@alpha.futurenet.co.za>
says...
> Hi!
>
> I am writing a CGI script which accepts input via QUERY_STRING.
> However, the input is only valid if it consists of EXACTLY 3 DIGITS! No
> more , no less, no other characters in front, after or in between the
> digits. Ive tried things such as:
>
> if ($ENV{'QUERY_STRING'} =~ /[0-9]\{3\}/)
if ($ENV{'QUERY_STRING'} =~ /^[0-9]{3}$/)
or (identically, but fewer keystrokes):
if ($ENV{QUERY_STRING} =~ /^\d{3}$/)
The start-of-string and end-of-string anchors ^ and $ are required by
your problem specification.
--
Larry Rosler
Hewlett-Packard Laboratories
http://www.hpl.hp.com/personal/Larry_Rosler/
lr@hpl.hp.com
------------------------------
Date: Mon, 13 Jul 1998 20:17:03 GMT
From: sowmaster@juicepigs.com (Bob Trieger)
Subject: Re: RegExps: Check if string consists of EXACTLY 3 digits ??
Message-Id: <6odq49$bp$1@strato.ultra.net>
karsten.no.123.spam@alpha.futurenet.co.za wrote:
-> Hi!
->
-> I am writing a CGI script which accepts input via QUERY_STRING.
-> However, the input is only valid if it consists of EXACTLY 3 DIGITS! No
-> more , no less, no other characters in front, after or in between the
-> digits. Ive tried things such as:
/^\d{3}$/
or
/^\d\d\d$/
HTH
Bob Trieger
sowmaster@juicepigs.com
" Cost a spammer some cash: Call 1-800-400-1972
Ext: 1949 and let the jerk that answers know
that his toll free number was sent as spam. "
------------------------------
Date: Mon, 13 Jul 1998 14:15:41 -0500
From: tadmc@flash.net (Tad McClellan)
Subject: Re: RegExps: Check if string consists of EXACTLY 3 digits ??
Message-Id: <tcmdo6.ue9.ln@localhost>
Karsten (karsten.no.123.spam@alpha.futurenet.co.za) wrote:
: I am writing a CGI script which accepts input via QUERY_STRING.
: However, the input is only valid if it consists of EXACTLY 3 DIGITS! No
: more , no less, no other characters in front, after or in between the
: digits. Ive tried things such as:
: if ($ENV{'QUERY_STRING'} =~ /[0-9]\{3\}/)
^ ^
^ ^ you don't need those
if ($ENV{'QUERY_STRING'} =~ /^\d{3}$/)
^^^ ^
--
Tad McClellan SGML Consulting
tadmc@metronet.com Perl programming
Fort Worth, Texas
------------------------------
Date: Mon, 13 Jul 1998 15:56:51 -0400
From: Gordon Avery <gavery@uu.net>
Subject: Sorting a 2-d array
Message-Id: <35AA6683.C06@uu.net>
Hi,
I'm trying to sort a 2-d array by the first element of each array and I
have had no luck. The best way I can come up with is:
sort { $array[$a][0] <=> $array[$b][0] } @array;
Thank you for any help.
Gordon Avery
gavery@uu.net
------------------------------
Date: Mon, 13 Jul 1998 16:22:07 -0400
From: comdog@computerdog.com (brian d foy)
Subject: Re: Sorting a 2-d array
Message-Id: <comdog-ya02408000R1307981622070001@news.panix.com>
Keywords: from just another new york perl hacker
In article <35AA6683.C06@uu.net>, Gordon Avery <gavery@uu.net> posted:
>Hi,
> I'm trying to sort a 2-d array by the first element of each array and I
>have had no luck. The best way I can come up with is:
>
>sort { $array[$a][0] <=> $array[$b][0] } @array;
remember what $a and $b are! they are the elements of the list
that you are sorting, not the indices of an array. perhaps you
meant
sort { $$a[0] <=> $$b[0] } @array;
or
sort { $a->[0] <=> $b->[0] } @array;
good luck :)
--
brian d foy <comdog@computerdog.com>
CGI Meta FAQ <URL:http://computerdog.com/CGI_MetaFAQ.html>
Comprehensive Perl Archive Network (CPAN) <URL:http://www.perl.com>
Perl Mongers Travel Deals! <URL:http://www.pm.org/travel.html>
------------------------------
Date: 13 Jul 1998 20:38:56 GMT
From: kortbein@iastate.edu (Josh Kortbein)
Subject: Re: Threads in Perl? NEWBIE ?
Message-Id: <6odr90$9al$1@news.iastate.edu>
Su Potter (spotter@remove-to-reply.ms.com) wrote:
: I'd like to know how how to create a thread in Perl and how it would be run.
: Please reply directly to spotter@ms.com aswell as the newsgroup, thanks.
In the current version of perl, you don't.
Surely Tom C. will say that you can do whatever you want with fork()
anyway.
Josh
--
__________________________________________
She had heard all about excluded middles;
they were bad shit, to be avoided.
- Thomas Pynchon
------------------------------
Date: 12 Jul 98 21:33:47 GMT (Last modified)
From: Perl-Request@ruby.oce.orst.edu (Perl-Users-Digest Admin)
Subject: Special: Digest Administrivia (Last modified: 12 Mar 98)
Message-Id: <null>
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------------------------------
End of Perl-Users Digest V8 Issue 3144
**************************************
