[31487] in Perl-Users-Digest
Perl-Users Digest, Issue: 2746 Volume: 11
daemon@ATHENA.MIT.EDU (Perl-Users Digest)
Thu Dec 31 21:09:46 2009
Date: Thu, 31 Dec 2009 18:09:12 -0800 (PST)
From: Perl-Users Digest <Perl-Users-Request@ruby.OCE.ORST.EDU>
To: Perl-Users@ruby.OCE.ORST.EDU (Perl-Users Digest)
Perl-Users Digest Thu, 31 Dec 2009 Volume: 11 Number: 2746
Today's topics:
Re: builtin array union intersection function <jurgenex@hotmail.com>
Does every perl statement has to end with ';'? <pengyu.ut@gmail.com>
Re: Does every perl statement has to end with ';'? (Jens Thoms Toerring)
Re: Does every perl statement has to end with ';'? <jurgenex@hotmail.com>
Re: Does every perl statement has to end with ';'? (Randal L. Schwartz)
Re: How to put '#!/usr/bin/env perl -w' at the beginnin <sysadmin@example.com>
Re: How to put '#!/usr/bin/env perl -w' at the beginnin <sysadmin@example.com>
Re: How to put '#!/usr/bin/env perl -w' at the beginnin <sysadmin@example.com>
Re: How to put '#!/usr/bin/env perl -w' at the beginnin <sysadmin@example.com>
Why the reversed result can not be printed correctly? <pengyu.ut@gmail.com>
Re: Why the reversed result can not be printed correctl charley@pulsenet.com
Re: Why the reversed result can not be printed correctl <john@castleamber.com>
Re: Why the reversed result can not be printed correctl <jurgenex@hotmail.com>
Re: Why the reversed result can not be printed correctl <tadmc@seesig.invalid>
Re: Why the reversed result can not be printed correctl <pengyu.ut@gmail.com>
Re: Why the reversed result can not be printed correctl <jurgenex@hotmail.com>
Re: Why the reversed result can not be printed correctl <jurgenex@hotmail.com>
Re: Why the reversed result can not be printed correctl <tadmc@seesig.invalid>
Digest Administrivia (Last modified: 6 Apr 01) (Perl-Users-Digest Admin)
----------------------------------------------------------------------
Date: Thu, 31 Dec 2009 08:19:01 -0800
From: Jürgen Exner <jurgenex@hotmail.com>
Subject: Re: builtin array union intersection function
Message-Id: <rhjpj5p5o30c7b1uqv1a12cto8bhou8t3e@4ax.com>
Peng Yu <pengyu.ut@gmail.com> wrote:
>There is some code fragment that can take union and intersection of
>two arrays.
>
>http://www.perlmonks.org/?node_id=64798
>
>But I'm looking for some functions in the library. Could somebody let
>me know if such things are available in the perl library?
What happened when you checked the FAQ for intersection?
perldoc -q intersection
What happened when you checked CPAN for array and intersection?
http://search.cpan.org/search?query=array+intersection&mode=module
jue
------------------------------
Date: Thu, 31 Dec 2009 12:16:27 -0800 (PST)
From: Peng Yu <pengyu.ut@gmail.com>
Subject: Does every perl statement has to end with ';'?
Message-Id: <17c41e81-60c4-4316-a845-509a77b20a38@p8g2000yqb.googlegroups.com>
It says in the following webpage http://www.comp.leeds.ac.uk/Perl/basic.html
and many other tutorials that every perl statement has to end with
';'. But it seems not to be the case (see the example below). I feel
that ';' in the last statement can be omitted. Could somebody point me
what the rules are?
$ ./semicolon.pl
Hello world!
pengy@morgan:~/test/perl$ cat semicolon.pl
#!/usr/bin/perl
print "Hello world!\n"
------------------------------
Date: 31 Dec 2009 20:38:43 GMT
From: jt@toerring.de (Jens Thoms Toerring)
Subject: Re: Does every perl statement has to end with ';'?
Message-Id: <7q4gejF6soU1@mid.uni-berlin.de>
Peng Yu <pengyu.ut@gmail.com> wrote:
> It says in the following webpage http://www.comp.leeds.ac.uk/Perl/basic.html
> and many other tutorials that every perl statement has to end with
> ';'. But it seems not to be the case (see the example below). I feel
> that ';' in the last statement can be omitted. Could somebody point me
> what the rules are?
> $ ./semicolon.pl
> Hello world!
> pengy@morgan:~/test/perl$ cat semicolon.pl
> #!/usr/bin/perl
> print "Hello world!\n"
The last line of a block (i.e. also code enclosed in curly braces)
doesn't need a terminating semicolon. On the other hand the website
is a tutorial and in tutorials you often find that not everything
is always spelled out completely at first for pedagogical reasons
- in this case giving a more complex rule at the very start probably
would have just confused some readers with an unimportant detail.
Regards, Jens
--
\ Jens Thoms Toerring ___ jt@toerring.de
\__________________________ http://toerring.de
------------------------------
Date: Thu, 31 Dec 2009 12:58:49 -0800
From: Jürgen Exner <jurgenex@hotmail.com>
Subject: Re: Does every perl statement has to end with ';'?
Message-Id: <as3qj5h69k7lv4a9pun7kj3v9356q4o9g9@4ax.com>
Peng Yu <pengyu.ut@gmail.com> wrote:
>It says in the following webpage http://www.comp.leeds.ac.uk/Perl/basic.html
>and many other tutorials that every perl statement has to end with
>';'.
Well, that's wrong.
>But it seems not to be the case (see the example below). I feel
>that ';' in the last statement can be omitted.
In Perl the ';' is a statement separator, not a statement terminator.
Therefore it is only required between two statement. However it is good
style to add it after the concluding statement in a block, too,
basically creating an empty statement, because then it is easier to add
another new final statement later without having to add the ';' in the
line above.
>Could somebody point me
>what the rules are?
perldoc perlsyn:
Simple Statements
[...] Every simple statement must be terminated with a
semicolon, unless it is the final statement in a block, in which
case
the semicolon is optional. (A semicolon is still encouraged if the
block
takes up more than one line, because you may eventually add another
line.) [...]
jue
------------------------------
Date: Thu, 31 Dec 2009 13:44:39 -0800
From: merlyn@stonehenge.com (Randal L. Schwartz)
Subject: Re: Does every perl statement has to end with ';'?
Message-Id: <86hbr67r94.fsf@blue.stonehenge.com>
>>>>> "Peng" == Peng Yu <pengyu.ut@gmail.com> writes:
Peng> It says in the following webpage http://www.comp.leeds.ac.uk/Perl/basic.html
Peng> and many other tutorials that every perl statement has to end with
Peng> ';'. But it seems not to be the case (see the example below). I feel
Peng> that ';' in the last statement can be omitted. Could somebody point me
Peng> what the rules are?
Yes, semicolons are required at the end of all statements.
However, the last semicolon of a compilation unit (file, block, or eval
string) may be omitted, because it is implied.
I recommend you include the terminating semicolon anyway, unless the beginning
of the compilation unit is also clearly on the same line.
For example:
@a = map { 2 + $_ } @input; # omit semicolon after expression
@a = map {
2 + $_; # include semicolon
} @input;
my $callback = sub { print "$_\n" }; # omit semicolon after print
my $callback = sub {
print "$_\n"; # include semicolon
};
sub foo {
print "hi ";
my $x = 2 + shift;
print "$x\n"; # semicolon here, since scope started 2 lines ago
} # a subroutine definition is not a statement, so no semicolon here
perl -e 'print "hello, no semicolon here\n"'
print "Just another Perl hacker,";
--
Randal L. Schwartz - Stonehenge Consulting Services, Inc. - +1 503 777 0095
<merlyn@stonehenge.com> <URL:http://www.stonehenge.com/merlyn/>
Smalltalk/Perl/Unix consulting, Technical writing, Comedy, etc. etc.
See http://methodsandmessages.vox.com/ for Smalltalk and Seaside discussion
------------------------------
Date: Thu, 31 Dec 2009 16:53:26 -0800
From: Wanna-Be Sys Admin <sysadmin@example.com>
Subject: Re: How to put '#!/usr/bin/env perl -w' at the beginning of a perl script?
Message-Id: <aIb%m.122$Ww.2@newsfe14.iad>
Tad McClellan wrote:
> Wanna-Be Sys Admin <sysadmin@example.com> wrote:
>> Kevin Collins wrote:
>>
>>>> Create a symbolic link for /usr/bin/perl to your non-standard
>>>> location and you should then be able to use the correct shebang in
>>>> your Perl scripts.
>>>
>>> This assumes you have rights to do that, which is often not the
>>> case...
>>>
>>
>> The Op's first post shows they have shell access, and I find that
>> assumption curious, as I've never seen a system prevent a user from
>> creating symbolic links
>
>
> Every system you've seen gives write permission
> on /usr/bin to ordinary users?
Nope. I never said this was for /usr/bin. The symlink would (or
should) be from their user's account path, and point that to wherever,
if they were going to use a symlink. This would allow them to run it
on whatever system, and just have to point the one symlink to the
system's Perl install.
> I have never seen a system that gives write permission
> on /usr/bin to ordinary users...
That's good, I've not either.
>
>> (even if it did, it would be unlikely a system
>> could prevent the user from executing the ln binary they could upload
>> themselves,
>
>
> errr, like a perl binary perhaps?
>
> perldoc -f symlink
That's one way, yes.
>
>> even if tehy didn't have access to the compilers). But, I
>> suppose it's possible. I just think they should call use warnings;
>> at the top
>
> We all think that (except the OP, who has hopefully been converted by
> now)
Right. No disagreement there.
>
>> and not have to mess with anything else, though I never, ever
>> use env in a script myself.
>
>
> You have not addressed the OP's primary problem.
I have.
> His binary is not at /usr/bin/perl and may in fact be in yet a
> third place when moved to another system.
Yep, so they need to update the shebang, or use env, or create a
symlink, or whatever. They were given several suggested options in
this thread.
--
Not really a wanna-be, but I don't know everything.
------------------------------
Date: Thu, 31 Dec 2009 16:55:47 -0800
From: Wanna-Be Sys Admin <sysadmin@example.com>
Subject: Re: How to put '#!/usr/bin/env perl -w' at the beginning of a perl script?
Message-Id: <oKb%m.123$Ww.103@newsfe14.iad>
Tad McClellan wrote:
> Wanna-Be Sys Admin <sysadmin@example.com> wrote:
>> Peng Yu wrote:
>>
>>> Since my perl is installed in a nonstandard location, I have to use
>>> '/
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>>> usr/bin/env perl'. I also what to use it with '-w'. I'm wondering
>>> how to do it.
>>>
>>> Currently, I have the following error.
>>>
>>> $ head -n 1 ./main.pl
>>> #!/usr/bin/env perl -w
>>> $ ./main.pl
>>> /usr/bin/env: perl -w: No such file or directory
>>
>> just use "use warnings;" which offers some advantages. Keep the env
>> the
>> same. Problem solved.
>
>
> Please re-read the problem statement...
I did, please re-read my response, among the other responses that I and
others gave. Anyway, I stated it they want to _keep_ the env shebang
setting and use warnings, that they _can_ do that, and to just use the
warnings module call instead. What is so confusing?
--
Not really a wanna-be, but I don't know everything.
------------------------------
Date: Thu, 31 Dec 2009 16:59:12 -0800
From: Wanna-Be Sys Admin <sysadmin@example.com>
Subject: Re: How to put '#!/usr/bin/env perl -w' at the beginning of a perl script?
Message-Id: <BNb%m.394$V_3.346@newsfe09.iad>
Dirk Heinrichs wrote:
> Ben Morrow wrote:
>
>>
>> Quoth Tad McClellan <tadmc@seesig.invalid>:
>>> Wanna-Be Sys Admin <sysadmin@example.com> wrote:
>>> > Peng Yu wrote:
>>> >
>>> >> Since my perl is installed in a nonstandard location, I have to
>>> >> use '/
>>> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>>> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>> Please re-read the solution offered...
>
> The offered solution was simply wrong,
It's not "wrong". The OP asked how they could work with their current
env solution. _I_ didn't suggest/recommend they use env. It's been
covered why it's not preferable. I gave them the appropriate response
to inform them how they can still enable warnings with their current
method, if they really want to or must somehow use it.
> so what Tad wrote is perfectly
> valid.
Not really.
> The right solution is to add the "nonstandard" location to
> $PATH, so that env can find perl there.
I would agree that's a better solution, assuming their script will be
able to use $PATH. They didn't say how many different ways they'll be
running the script. It might be CGI and CLI, so env might be a better
solution than modifying $PATH.
> The problem has nothing to do with "-w" at all!!!
Actually, it did. The OP's question was how to pass -w to the script.
My response simply said that "if that's how you want to run it", to
then just use warnings; instead.
> Bye...
>
> Dirk
Cya.
--
Not really a wanna-be, but I don't know everything.
------------------------------
Date: Thu, 31 Dec 2009 17:06:55 -0800
From: Wanna-Be Sys Admin <sysadmin@example.com>
Subject: Re: How to put '#!/usr/bin/env perl -w' at the beginning of a perl script?
Message-Id: <QUb%m.395$V_3.333@newsfe09.iad>
Wanna-Be Sys Admin wrote:
> Anyway, I stated it they
^^
*if
--
Not really a wanna-be, but I don't know everything.
------------------------------
Date: Thu, 31 Dec 2009 11:45:29 -0800 (PST)
From: Peng Yu <pengyu.ut@gmail.com>
Subject: Why the reversed result can not be printed correctly?
Message-Id: <2492b6dd-3321-4c42-9435-7a4d8a566261@m16g2000yqc.googlegroups.com>
Only the first statement prints the reversed result correctly. I'm
confused why the other three don't print as I expected. How to print
the reversed result without using the intermediate variable $rstring?
$ cat reverse.pl
#!/usr/bin/perl
use warnings;
$string = "abc";
$rstring=reverse($string);
print "$rstring\n";
print reverse($string), "\n";
print(reverse($string), "\n");
print((reverse($string)), "\n");
$ ./reverse.pl
cba
abc
abc
abc
------------------------------
Date: Thu, 31 Dec 2009 12:27:44 -0800 (PST)
From: charley@pulsenet.com
Subject: Re: Why the reversed result can not be printed correctly?
Message-Id: <a91265df-6d8b-4ffb-b4be-1949b4702b1f@m3g2000yqf.googlegroups.com>
On Dec 31, 2:45=A0pm, Peng Yu <pengyu...@gmail.com> wrote:
> Only the first statement prints the reversed result correctly. I'm
> confused why the other three don't print as I expected. How to print
> the reversed result without using the intermediate variable $rstring?
>
> $ cat reverse.pl
> #!/usr/bin/perl
>
> use warnings;
>
> $string =3D "abc";
> $rstring=3Dreverse($string);
> print "$rstring\n";
> print reverse($string), "\n";
> print(reverse($string), "\n");
> print((reverse($string)), "\n");
>
> $ ./reverse.pl
> cba
> abc
> abc
> abc
Hello Peng,
You need to consider that the print operator expects a list. The text
below is copied from 'perldoc -f print'.
Because print takes a LIST, anything in the LIST is evaluated in list
context...
In your code,
print reverse($string), "\n";
print is expecting a list, and so reverse tries to return a list in
reverse order. However, the only item in the list is '$string', so it
gives that to print.
print scalar reverse($string), "\n";
C:\perlp>perldoc -f reverse
reverse LIST
In list context, returns a list value consisting of the
elements
of LIST in the opposite order. In scalar context,
concatenates
the elements of LIST and returns a string value with all
characters in the opposite order.
Chris
------------------------------
Date: Thu, 31 Dec 2009 14:43:02 -0600
From: John Bokma <john@castleamber.com>
Subject: Re: Why the reversed result can not be printed correctly?
Message-Id: <87hbr6q3hl.fsf@castleamber.com>
Peng Yu <pengyu.ut@gmail.com> writes:
> Only the first statement prints the reversed result correctly. I'm
> confused why the other three don't print as I expected. How to print
> the reversed result without using the intermediate variable $rstring?
>
> $ cat reverse.pl
> #!/usr/bin/perl
>
> use warnings;
>
> $string = "abc";
> $rstring=reverse($string);
> print "$rstring\n";
> print reverse($string), "\n";
> print(reverse($string), "\n");
> print((reverse($string)), "\n");
>
> $ ./reverse.pl
> cba
> abc
> abc
> abc
john@ecce:~$ perl -e 'print reverse("abc"), "\n"'
abc
john@ecce:~$ perl -e 'print scalar(reverse("abc")), "\n"'
cba
perl -e 'print reverse("abc") . "\n"'
cba
perldoc -f reverse
reverse LIST
In list context, returns a list value consisting of the
elements of LIST in the opposite order. In scalar context,
concatenates the elements of LIST and returns a string value
with all characters in the opposite order.
--
John Bokma
Read my blog: http://johnbokma.com/
Hire me (Perl/Python): http://castleamber.com/
------------------------------
Date: Thu, 31 Dec 2009 12:54:02 -0800
From: Jürgen Exner <jurgenex@hotmail.com>
Subject: Re: Why the reversed result can not be printed correctly?
Message-Id: <bn3qj5h1ilestm5s42bdankivm7kjc112b@4ax.com>
Peng Yu <pengyu.ut@gmail.com> wrote:
>Only the first statement prints the reversed result correctly. I'm
>confused why the other three don't print as I expected. How to print
>the reversed result without using the intermediate variable $rstring?
>
>$ cat reverse.pl
>#!/usr/bin/perl
>
>use warnings;
>
>$string = "abc";
>$rstring=reverse($string);
>print "$rstring\n";
>print reverse($string), "\n";
>print(reverse($string), "\n");
>print((reverse($string)), "\n");
Use reverse() in scalar instead of in list context:
print scalar(reverse($string)), "\n";
In your examples you are just swapping the position of the string and
the "\n".
jue
------------------------------
Date: Thu, 31 Dec 2009 15:31:01 -0600
From: Tad McClellan <tadmc@seesig.invalid>
Subject: Re: Why the reversed result can not be printed correctly?
Message-Id: <slrnhjq5qd.crv.tadmc@tadbox.sbcglobal.net>
Jürgen Exner <jurgenex@hotmail.com> wrote:
> Peng Yu <pengyu.ut@gmail.com> wrote:
>>Only the first statement prints the reversed result correctly. I'm
>>confused why the other three don't print as I expected. How to print
>>the reversed result without using the intermediate variable $rstring?
>>
>>$ cat reverse.pl
>>#!/usr/bin/perl
>>
>>use warnings;
>>
>>$string = "abc";
>>$rstring=reverse($string);
>>print "$rstring\n";
>>print reverse($string), "\n";
>>print(reverse($string), "\n");
>>print((reverse($string)), "\n");
>
> Use reverse() in scalar instead of in list context:
> print scalar(reverse($string)), "\n";
That is correct.
> In your examples you are just swapping the position of the string and
> the "\n".
That is not correct, as the newline is not an argument to reverse()...
(reversing the order of a one-element list is Really Easy :-)
--
Tad McClellan
email: perl -le "print scalar reverse qq/moc.liamg\100cm.j.dat/"
------------------------------
Date: Thu, 31 Dec 2009 14:36:08 -0800 (PST)
From: Peng Yu <pengyu.ut@gmail.com>
Subject: Re: Why the reversed result can not be printed correctly?
Message-Id: <77862eb4-fcb3-4bf4-a8e0-f1d21154e79f@s3g2000yqs.googlegroups.com>
On Jan 1, 2:43=A0pm, John Bokma <j...@castleamber.com> wrote:
> Peng Yu <pengyu...@gmail.com> writes:
> > Only the first statement prints the reversed result correctly. I'm
> > confused why the other three don't print as I expected. How to print
> > the reversed result without using the intermediate variable $rstring?
>
> > $ cat reverse.pl
> > #!/usr/bin/perl
>
> > use warnings;
>
> > $string =3D "abc";
> > $rstring=3Dreverse($string);
> > print "$rstring\n";
> > print reverse($string), "\n";
> > print(reverse($string), "\n");
> > print((reverse($string)), "\n");
>
> > $ ./reverse.pl
> > cba
> > abc
> > abc
> > abc
>
> john@ecce:~$ perl -e 'print reverse("abc"), "\n"'
> abc
> john@ecce:~$ perl -e 'print scalar(reverse("abc")), "\n"'
> cba
> perl -e 'print reverse("abc") . "\n"'
> cba
>
> perldoc -f reverse
> =A0 =A0 =A0 =A0reverse LIST
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0In list context, returns a list value cons=
isting of the
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0elements of LIST in the opposite order. =
=A0In scalar context,
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0concatenates the elements of LIST and retu=
rns a string value
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0with all characters in the opposite order.
I'm wondering how to define a user function that is context dependent.
Could you give me a simple example?
------------------------------
Date: Thu, 31 Dec 2009 15:40:58 -0800
From: Jürgen Exner <jurgenex@hotmail.com>
Subject: Re: Why the reversed result can not be printed correctly?
Message-Id: <4jdqj5tvi6uhh1q65o9p4cejkour7h62sb@4ax.com>
Peng Yu <pengyu.ut@gmail.com> wrote:
>I'm wondering how to define a user function that is context dependent.
perldoc -f wantarray
jue
------------------------------
Date: Thu, 31 Dec 2009 15:41:35 -0800
From: Jürgen Exner <jurgenex@hotmail.com>
Subject: Re: Why the reversed result can not be printed correctly?
Message-Id: <kkdqj5t9rsc0pr40p1gi98rb6463q68108@4ax.com>
Tad McClellan <tadmc@seesig.invalid> wrote:
>Jürgen Exner <jurgenex@hotmail.com> wrote:
>> Peng Yu <pengyu.ut@gmail.com> wrote:
>>>Only the first statement prints the reversed result correctly. I'm
>>>confused why the other three don't print as I expected. How to print
>>>the reversed result without using the intermediate variable $rstring?
>>>
>>>$ cat reverse.pl
>>>#!/usr/bin/perl
>>>
>>>use warnings;
>>>
>>>$string = "abc";
>>>$rstring=reverse($string);
>>>print "$rstring\n";
>>>print reverse($string), "\n";
>>>print(reverse($string), "\n");
>>>print((reverse($string)), "\n");
>>
>> Use reverse() in scalar instead of in list context:
>> print scalar(reverse($string)), "\n";
>
>
>That is correct.
>
>
>> In your examples you are just swapping the position of the string and
>> the "\n".
>
>That is not correct, as the newline is not an argument to reverse()...
Ooops, you are right of course.
jue
------------------------------
Date: Thu, 31 Dec 2009 18:43:21 -0600
From: Tad McClellan <tadmc@seesig.invalid>
Subject: Re: Why the reversed result can not be printed correctly?
Message-Id: <slrnhjqh31.dec.tadmc@tadbox.sbcglobal.net>
Peng Yu <pengyu.ut@gmail.com> wrote:
> I'm wondering how to define a user function that is context dependent.
> Could you give me a simple example?
-----------------------
#!/usr/bin/perl
use warnings;
use strict;
my $rstring = context();
print context(), "\n";
sub context {
if ( wantarray )
{ warn "list context\n" }
else
{ warn "scalar context\n" }
}
-----------------------
--
Tad McClellan
email: perl -le "print scalar reverse qq/moc.liamg\100cm.j.dat/"
------------------------------
Date: 6 Apr 2001 21:33:47 GMT (Last modified)
From: Perl-Users-Request@ruby.oce.orst.edu (Perl-Users-Digest Admin)
Subject: Digest Administrivia (Last modified: 6 Apr 01)
Message-Id: <null>
Administrivia:
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------------------------------
End of Perl-Users Digest V11 Issue 2746
***************************************
