How to in perl
Bill H
there has to be an easier way of trimming the spaces off the begining
and ending of a variable. I use the following which is basically a
translation of a BASIC routine I have used for years:
while(substr($temp,0,1) eq " ")
{
$temp = substr($temp,1);
}
while(substr($temp,-1) eq " ")
{
$temp = substr($temp,0,length($temp) - 1);
}
There has to be a simpler way in perl than this.
Bill H
A. Sinan Unur
news:1135016634.4...@g14g2000cwa.googlegroups.com:
> Subject: How to in perl
Please see
> I do a lot of small routines in perl for manipulating data and know
> there has to be an easier way of trimming the spaces off the begining
> and ending of a variable. I use the following which is basically a
> translation of a BASIC routine I have used for years:
>
> while(substr($temp,0,1) eq " ")
> {
> $temp = substr($temp,1);
> }
> while(substr($temp,-1) eq " ")
> {
> $temp = substr($temp,0,length($temp) - 1);
> }
#!/usr/bin/perl
use strict;
use warnings;
my $str = q{ sdfkj sdkfj };
$str =~ s/ \A \s+ //x;
$str =~ s/ \s+ \z //x;
print "-$str-\n";
__END__
Sinan
--
A. Sinan Unur <1u...@llenroc.ude.invalid>
(reverse each component and remove .invalid for email address)
comp.lang.perl.misc guidelines on the WWW:
http://mail.augustmail.com/~tadmc/clpmisc/clpmisc_guidelines.html
Matt Garrish
"Bill H" <bi...@ts1000.us> wrote in message
news:1135016634.4...@g14g2000cwa.googlegroups.com...
A regular expression will do:
$temp =~ s/^\s*(.*?)\s*$/$1/;
Of course, this gets rid of any type leading or trailing of whitespace,
which may or may not be what you want. You can switch \s with a space if it
does.
Matt
use...@davidfilmer.com
> How to in perl
Please see the posting guidelines which Sinan referred you to in an
earlier reply
> there has to be an easier way of trimming the spaces off the begining
> and ending of a variable...
There are many ways to do it in Perl. Here's my usual:
s/^\s*//, s/\s+$// for $foo;
Gunnar Hjalmarsson
> Bill H wrote:
>>there has to be an easier way of trimming the spaces off the begining
>>and ending of a variable.
>
>
> $temp =~ s/^\s*(.*?)\s*$/$1/;
Hrrmm..
perldoc -q "strip blank"
--
Gunnar Hjalmarsson
Email: http://www.gunnar.cc/cgi-bin/contact.pl
Matt Garrish
"Gunnar Hjalmarsson" <nor...@gunnar.cc> wrote in message
news:40ogvmF...@individual.net...
> Matt Garrish wrote:
>> Bill H wrote:
>>>there has to be an easier way of trimming the spaces off the begining
>>>and ending of a variable.
>>
>> A regular expression will do:
>>
>> $temp =~ s/^\s*(.*?)\s*$/$1/;
>
> Hrrmm..
>
> perldoc -q "strip blank"
>
Slow and destructive has never bothered me (though if you're running it
(tens of) thousands of times I suppose you might), and the embedded
newlines, if likely, can be easily handled with /s. Whatever you like...
Matt
Dr.Ruud
> s/^\s*//, s/\s+$// for $foo;
Is there a special reason for ^\s*,
or did you mean ^\s+ ?
--
Affijn, Ruud
"Gewoon is een tijger."
use...@davidfilmer.com
> use...@DavidFilmer.com:
>
> > s/^\s*//, s/\s+$// for $foo;
>
> Is there a special reason for ^\s*,
> or did you mean ^\s+ ?
Does it make a difference in this situation?
John Bokma
I think yes, but you have to benchmark it. I would use \s+ for both since
I want to drop one or more spaces (and not zero or more)
Strikes me as odd to use \s* for one and \s+ for the other.
--
John Small Perl scripts: http://johnbokma.com/perl/
Perl programmer available: http://castleamber.com/
I ploink googlegroups.com :-)
Dr.Ruud
> Dr.Ruud:
>> use...@DavidFilmer.com:
Beyond that it hurts my eyes? Let's find out.
John W. Krahn
It may not make much of a difference but it does make a difference. \s* will
always match so the replacement will always take place while \s+ will only
match if there is whitespace present so the replacement will not take place if
there is no whitespace.
John
--
use Perl;
program
fulfillment
Jürgen Exner
Is there anything wrong with the answer in the FAQ ("perldoc -q space"):
"How do I strip blank space from the beginning/end of a string?"
jue
Anno Siegel
> use...@DavidFilmer.com:
> > Dr.Ruud:
> >> use...@DavidFilmer.com:
>
> >>> s/^\s*//, s/\s+$// for $foo;
> >>
> >> Is there a special reason for ^\s*,
> >> or did you mean ^\s+ ?
> >
> > Does it make a difference in this situation?
>
> Beyond that it hurts my eyes? Let's find out.
Yes, let's. Benchmark (appended below) shows "+" faster than "*".
The speedup is most noticeable (a factor of almost 2) when there
are no blanks to trim and goes down to 1.2 for an average of 15
blanks front and rear. Makes sense.
So, in the rather unlikely case that the time for trimming blanks
matters at all, the difference may be significant.
Anno
-----------------------------------------------------------------
#!/usr/bin/perl
use strict; use warnings; $| = 1; # @^~`
use Vi::QuickFix;
use Benchmark qw( cmpthese);
use constant SIZE => 20;
my @none = ( qw( alpha beta gamma delta)) x SIZE;
my @few = map blanks( 3) . $_ . blanks( 3), @none;
my @many = map blanks( 30) . $_ . blanks( 30), @none;
goto bench;
check:
for ( 1 .. 7 ) {
for ( shift( @none), shift( @few), shift( @many) ) {
print "|$_| -> ";
s/^\s+//, s/\s+$//;
print " |$_|\n";
}
print "--------------------\n";
}
exit;
bench:
print "No Blanks:\n";
my @data = @none;
cmpthese -1, {
plus => sub { s/^\s+//, s/\s+$// for map "$_", @data },
aster => sub { s/^\s*//, s/\s*$// for map "$_", @data },
};
print "\nFew Blanks:\n";
@data = @few;
cmpthese -1, {
plus => sub { s/^\s+//, s/\s+$// for map "$_", @data },
aster => sub { s/^\s*//, s/\s*$// for map "$_", @data },
};
print "\nMany Blanks:\n";
@data = @many;
cmpthese -1, {
plus => sub { s/^\s+//, s/\s+$// for map "$_", @data },
aster => sub { s/^\s*//, s/\s*$// for map "$_", @data },
};
########################################################################
sub blanks { ' ' x rand shift }
--
If you want to post a followup via groups.google.com, don't use
the broken "Reply" link at the bottom of the article. Click on
"show options" at the top of the article, then click on the
"Reply" at the bottom of the article headers.
Dr.Ruud
> Dr.Ruud:
>> use...@DavidFilmer.com:
>>> Dr.Ruud:
>>>> use...@DavidFilmer.com:
>>>>> s/^\s*//, s/\s+$// for $foo;
>>>>
>>>> Is there a special reason for ^\s*,
>>>> or did you mean ^\s+ ?
>>>
>>> Does it make a difference in this situation?
>>
>> Beyond that it hurts my eyes? Let's find out.
>
> Yes, let's. Benchmark (appended below) shows "+" faster than "*".
> The speedup is most noticeable (a factor of almost 2) when there
> are no blanks to trim and goes down to 1.2 for an average of 15
> blanks front and rear. Makes sense.
Yes, thanks for that. I inserted a substr() approach like:
my ($i1, $i2);
for ( $i1 = 0 ; ' ' eq substr($_, $i1, 1) ; $i1++ ) {};
for ( $i2 = length() -1 ; ($i2 > $i1) && (' ' eq substr($_, $i2, 1)) ;
$i2-- ) {};
$_ = substr($_, $i1, $i2 - $i1 +1);
and that performed dramatically worse.
> So, in the rather unlikely case that the time for trimming blanks
> matters at all, the difference may be significant.
There's more to it than time: with s/^\s*// the data will always be
touched (even when the returned list of s/// is not used, unless perl
includes an optimization for that situation).
Tad McClellan
> Subject: How to in perl
Please put the subject of your article in the Subject of your article.
--
Tad McClellan SGML consulting
ta...@augustmail.com Perl programming
Fort Worth, Texas
Eckstein C.
> Bill H <bi...@ts1000.us> wrote:
>
>> Subject: How to in perl
>
>
> Please put the subject of your article in the Subject of your article.
He did have it in the subject of his article...
A. Sinan Unur
news:40qq92F...@individual.net:
What he had in the subject of this article was "How to in perl". That
was not what the OP's article was about. The OP's article was about
trimming leading and trailing spaces from a string. Hence, an
appropriate subject line would have been:
Subject: How to trim leading/trailing spaces
But, of course, if the OP had actually read the FAQ, then he would have
known the answer to that question.
And, if you had read the posting guidelines, you would have known what
Tad meant, instead of this silly post.
Bill H
answer.
Didn't know:
1) there was a rule on how to post messages
2) that there was even a perl usenet till I stumbled upon it
3) asking a basic question would get everyone in such an uproar
Maybe I should just go back to searching the internet for information
on how to do something in perl?
All the other usenet groups I post on allow asking questions and
posting opinions. The reception I got here made me feel as if I was in
a upscale restaurant and used the wrong fork to eat my salad.
Bill H
Bill H
http://mail.augustmail.com/~tadmc/clpmisc/clpmisc_guidelines.html
And saw this almost immedietly:
A note to newsgroup ``regulars'':
Do not use these guidelines as a "license to flame" or other
meanness. It is possible that a poster is unaware of things
discussed here. Give them the benefit of the doubt, and just
help them learn how to post, rather than assume
Maybe you guys should read them also
Paul Lalli
Please point out, specifically, which response you believe was a flame,
or otherwise "meanness". Reviewing the thread, I see nothing of the
sort. I see bluntness, yes, but not cruelty, rudeness, or flaming.
Paul Lalli
Bill H
me, in perl terms:
@dbf = split(/\./,qq~Do not use these guidelines as a "license to
flame" or other meanness. It is possible that a poster is unaware of
things discussed here. Give them the benefit of the doubt, and just
help them learn how to post, rather than assume ~);
print $dbf[1];
Bill H
Paul Lalli
Sigh. And still you refuse to quote context, even after reading the
guidlines? At this point, I now have to assume you're intentionally
being rude.
Regardless, I was asking you which response you got from the "regulars"
(myself included) you believe violates that piece of the guidelines.
You have responded by simply quoting the guidelines again, rather than
answering my question.
Paul Lalli
Eric Schwartz
> I just cut and pasted from the Guidelines. The part that stood out to
> me, in perl terms:
Bill,
1) Please quote some context; not everybody uses Google, and not all
posts are guaranteed to arrive, much less arrive in the order they
were sent. I have several times seen responses to posts that
haven't shown up yet-- if there is no context, I have no idea what
the responses are about.
2) Paul was asking what responses the OP got that you felt were flames
or otherwise mean. You responded by requoting the part of the
Guidelines that requests people not flame or be otherwise mean. If
you're interested in being cute, and scoring points, then by all
means continue posting in that vein. But if you actually wish to
have a dialogue, and possibly change things, you have to take
people seriously when they ask for information, and provide it.
-=Eric
Bill H
every day. That part that "bothered" me was this (will quote it)
=============
What he had in the subject of this article was "How to in perl". That
was not what the OP's article was about. The OP's article was about
trimming leading and trailing spaces from a string. Hence, an
appropriate subject line would have been:
Subject: How to trim leading/trailing spaces
But, of course, if the OP had actually read the FAQ, then he would have
known the answer to that question.
Sinan
===========================
But maybe I went a little overboard on the response. Where I live
around here there is not a soul that knows perl. Over the past 6 years
I have been using perl exclusively on my web hosting company and have
written some very complex programs, but since I taught myself with a
Basic, Asm and C background my programming style is not always the most
efficient, hence the original post. Up until today I didn't know I
could get to the perldoc's from the Dos prompt when I am writting perl
code. I have the complete docs printed out, it is 500+ pages long and
very hard to find information in, so I have learned how to program in
it hit / miss. When I came upon this usenet group I thought here was a
great place for me to ask those questions about how to do things right.
Bill H
use...@davidfilmer.com
> Didn't know:
>
> 1) there was a rule on how to post messages
We know you didn't know. That's why we let you know. We weren't being
"mean" to tell you - we were trying to be helpful.
> 2) that there was even a perl usenet till I stumbled upon it
I'm not sure what you mean. There are usenet groups for nearly every
subject (and several for Perl). This particular group is (by far) the
most active for Perl, and many of the "regulars" are expert Perl
programmers (you may recognize several of the posters here - their
names might be on the covers of your Perl books, or they may be the
authors of CPAN modules that you use).
> 3) asking a basic question would get everyone in such an uproar
What uproar? I didn't notice any uproar. If there was any "uproar" at
all, it was in follow-ups to my own post, as to whether it mattered if
my code suggestion used a "*" or a "+" (I thought it wouldn't matter -
I was wrong - and I'm happy to know that!)
> Maybe I should just go back to searching the internet for information
> on how to do something in perl?
The Internet is a great resource. I usually Google around before asking
a question in usenet. Newsgroups should normally be the last resort
when trying to find an answer.
> All the other usenet groups I post on allow asking questions and
> posting opinions. The reception I got here made me feel as if I was in
> a upscale restaurant and used the wrong fork to eat my salad.
Do you feel anyone was mean or rude to you? I must have missed that
reply. Even though you asked a question which is readily answered in
the FAQ (bad ettiquete in ANY newsgroup, as I'm sure you would agree),
you still received several expert answers (and corrected input to my
own not-so-expert answer). Even Sinan posted some code (and I don't
believe I have ever known Sinan to post code in reply to a question
that is already answered in the Perl FAQ).
Tad McClellan
> Sorry to have stepped on toes, thank you for at least giving me an
> answer.
>
> Didn't know:
>
> 1) there was a rule on how to post messages
Many of the same rules exist in thousands of newsgroups.
> 3) asking a basic question would get everyone in such an uproar
You seem to have misidentified the source of the uproar.
There is no uproar when someone asks a basic question.
There is an uproar when someone asks a Frequently Asked Question
(because it will be assumed that you didn't check the FAQ at all).
There is an uproar in thousands of newsgroups when someone
asks a FAQ.
There is an uproar when a poster cannot be troubled to come up
with a useful Subject line.
Consider your peers for a moment. When somebody else needs to
know how to strip spaces are they going to look at a thread
with the Subject you chose?
Choosing a good Subject makes it easier for other people to
find answers.
Making it easier for others to find answers does not seem
like much of a price to pay for getting an answer to your question...
> Maybe I should just go back to searching the internet for information
> on how to do something in perl?
That would be easier for you to do if folks chose meaningful Subjects.
> All the other usenet groups I post on allow asking questions and
They allow asking Frequently Asked Questions?
I have never seen such a newsgroup.
> The reception I got here made me feel as if I was in
> a upscale restaurant and used the wrong fork to eat my salad.
Then use the right fork, and get free consulting in return!
That's a bargain!
use...@davidfilmer.com
> I didn't know that about the timing of the posts, learn something new
OK, _NOW_ you're starting to use up your "quota" of goodwill (once your
quota is used up, you can expect to be flamed or - worse - killfiled).
I can only assume you don't understand what is meant by "quote
context."
When you reply to a message, it's common usenet courtesy to quote the
name/handle of the person who replied, and enough of the reply to
establish context so we have SOME IDEA what you're replying to.
Here's an analogy: Suppose you're having a conversation with "Joe" on
the telephone. Now suppose there are other people in the room that you
wish to know about the conversation (and maybe get their input). If
Joe starts talking about floozling a giget, you would need to say, "Joe
asks how we can floozle the giget," so that when you start talking
about how to floozle it, people understand what you're discussing. You
don't just dive into the discussion about the giget with Joe, because
nobody else in the room knows what you're responding to - they only
hear half the conversation.
You see what I did at the top of the screen? I cited your handle and
quoted the bit of your post that I'm discussing in this reply (namely
your refusal to quote context in your replies). That's what we mean by
"quote context."
If you're using Google Groups, don't use the "reply" link at the BOTTOM
of the message. Click "Show Options" at the TOP of the message (next to
the poster's handle), and then click "Reply" from the expanded options
that appear. If you do this, Google will automatically provide the
proper quoting style (though you should snip for brevity as
appropriate).
See previous messages in this thread for examples of proper context
quoting.
Tad McClellan
So, which poster in this thread flamed or displayed other meanness?
Tad McClellan
> I didn't know that about the timing of the posts, learn something new
> every day. That part that "bothered" me was this (will quote it)
>
>=============
> What he had in the subject of this article was "How to in perl". That
> was not what the OP's article was about. The OP's article was about
> trimming leading and trailing spaces from a string. Hence, an
> appropriate subject line would have been:
>
> Subject: How to trim leading/trailing spaces
>
> But, of course, if the OP had actually read the FAQ, then he would have
>
> known the answer to that question.
>
>
> Sinan
>===========================
What was it about that reply bothered you?
An illustration of how your Subject could have been better?
That is more helpful than you realize.
Being taken to task for not checking the Perl FAQ before
posting to the Perl newsgroup?
> I thought here was a
> great place for me to ask those questions about how to do things right.
How to make posts right involves choosing a meaningful Subject
and quoting context in followups.
So you were right, this is a great place for you to ask those questions
about how to do things right.
(but folks kinda expect that you will start doing it right once
you learn what "right" is.
)
A. Sinan Unur
news:1135120321.2...@g43g2000cwa.googlegroups.com:
> I didn't know that about the timing of the posts, learn something new
> every day. That part that "bothered" me was this (will quote it)
>
> =============
> What he had in the subject of this article was "How to in perl". That
> was not what the OP's article was about. The OP's article was about
> trimming leading and trailing spaces from a string. Hence, an
> appropriate subject line would have been:
>
> Subject: How to trim leading/trailing spaces
>
> But, of course, if the OP had actually read the FAQ, then he would
> have known the answer to that question.
>
> Sinan
> ===========================
It looks like, just as you do not quote context, you don't read the
context of the message either. You can see my response in context at:
http://groups.google.com/group/comp.lang.perl.misc/msg/819371647ffb6ae6
In addition, I am afraid you did not read my original response to your
question either.
> so I have learned how to program in it hit / miss.
That is not a good way to learn programming. You should have asked your
questions six years ago.
> When I came upon this usenet group I thought here was a great
> place for me to ask those questions about how to do things
> right.
Absolutely. But it looks like you do not like being corrected. That
might result in fewer people being willing to read your questions.
Vronans
> Bill H <bi...@ts1000.us> wrote:
>> Sorry to have stepped on toes, thank you for at least giving me an
>> answer.
>>
>> Didn't know:
>>
>> 1) there was a rule on how to post messages
>
> Many of the same rules exist in thousands of newsgroups.
Many not in the same way as here.
>> All the other usenet groups I post on allow asking questions and
>
> They allow asking Frequently Asked Questions?
Many do not make such huge deal about (though some might.) But meny os
called faq's are a variation of a documented FAQ, but often there is
some reason, like something unique that factors in. I've seen many such
question unfairly shot down in this group, but turn into interesting
discussions.
> I have never seen such a newsgroup.
Bollocks. Unless you only read this one...
Bill H
Tad McClellan wrote:
> Bill H <bi...@ts1000.us> wrote:
> > I didn't know that about the timing of the posts, learn something new
> > every day. That part that "bothered" me was this (will quote it)
> >
> >=============
> > What he had in the subject of this article was "How to in perl". That
> > was not what the OP's article was about. The OP's article was about
> > trimming leading and trailing spaces from a string. Hence, an
> > appropriate subject line would have been:
> >
> > Subject: How to trim leading/trailing spaces
> >
> > But, of course, if the OP had actually read the FAQ, then he would have
> >
> > known the answer to that question.
> >
> >
> > Sinan
> >===========================
>
>
> What was it about that reply bothered you?
>
> An illustration of how your Subject could have been better?
>
> That is more helpful than you realize.
Yes maybe the subject could have better written, but I did get an
answer back (actually a number of different ones) so for that, thank
you.
>
> Being taken to task for not checking the Perl FAQ before
> posting to the Perl newsgroup?
If you mean a FAQ for this newsgroup - sure would have read it - if I
had known it existed.
>
>
> > I thought here was a
> > great place for me to ask those questions about how to do things right.
>
>
> How to make posts right involves choosing a meaningful Subject
> and quoting context in followups.
At the time I was not concerned about making a "right" post, I was
hoping to find a simpler way of doing things.
I did a search on this group using "remove spaces" and looked at the
results sorted by date. Last time someone asked the question I did was
9/15/02 (here is the link http://tinyurl.com/7lnuc ) and there a number
of repsonses (which are different then these given) before someone
finally chimed in about reading the faq.
I notice a number of posts from the PerlFAQ Server. If this is an
automated system, maybe it should post on a daily basis something like:
Newbies: Read this before posting
Jürgen Exner
> I notice a number of posts from the PerlFAQ Server. If this is an
> automated system,
Yes, it is.
> maybe it should post on a daily basis something
> like: Newbies: Read this before posting
Well, guess what, the Posting Guidelines are posted twice weekly already.
Somehow you must have missed them somehow during your lurking time.
jue
Tad McClellan
> Yes maybe the subject could have better written,
"maybe"?
> If you mean a FAQ for this newsgroup - sure would have read it - if I
> had known it existed.
It is your fault for not checking to see if a FAQ exists, not ours.
Typing
perl faq
into the little box at google.com shows it lots of places.
You made a social blunder. Your attempts at justifications to
wiggle out of owning up to it is more annoying than the
original blunder.
> At the time I was not concerned about making a "right" post,
I give up.
So long!
> I notice a number of posts from the PerlFAQ Server. If this is an
> automated system, maybe it should post on a daily basis something like:
> Newbies: Read this before posting
You must be new here.
That has been tried before, it doesn't work because they still
won't (or don't) read it.
There is however a set of Posting Guidelines that are posted here
twice each week. It lists checking the FAQ before posting right
at the top.
Did you read it before posting? (rhetorical question)
See? It doesn't work.
A. Sinan Unur
@news.astound.net:
> Tad McClellan wrote:
>> They allow asking Frequently Asked Questions?
>
> Many do not make such huge deal about (though some might.) But meny os
> called faq's are a variation of a documented FAQ,
Huh ??? I cannot parse this sentence.
> I've seen many such question unfairly shot down in this group,
> but turn into interesting discussions.
What do you mean?
A. Sinan Unur
>
> Tad McClellan wrote:
>> Bill H <bi...@ts1000.us> wrote:
>> > I didn't know that about the timing of the posts, learn something
>> > new every day. That part that "bothered" me was this (will quote
>> > it)
>> >
>> >=============
>> > What he had in the subject of this article was "How to in perl".
>> > That was not what the OP's article was about. The OP's article was
>> > about trimming leading and trailing spaces from a string. Hence, an
>> > appropriate subject line would have been:
>> >
>> > Subject: How to trim leading/trailing spaces
>> >
>> > But, of course, if the OP had actually read the FAQ, then he would
>> > have
>> >
>> > known the answer to that question.
>> >
>> >
>> > Sinan
>> >===========================
>>
>>
>> What was it about that reply bothered you?
>>
>> An illustration of how your Subject could have been better?
>>
>> That is more helpful than you realize.
>
> Yes maybe the subject could have better written, but I did get an
> answer back
From me, as well.
> If you mean a FAQ for this newsgroup - sure would have read it - if I
> had known it existed.
That is really lame. You are posting from Google, for the sake of
everything that's holy in the land of unicorns! How much effort
does it take to type the words
perl faq
in that search box?
> At the time I was not concerned about making a "right" post, I was
> hoping to find a simpler way of doing things.
I see. So, your needs trump everything else, right?
> I notice a number of posts from the PerlFAQ Server. If this is an
> automated system, maybe it should post on a daily basis something
> like: Newbies: Read this before posting
You could have thanked for the responses to your question, said,
"oops, my bad" for not checking the FAQ, and moved on.
But you did not.
Bye bye.