Re: Count Function?
Hi Paul,
In article <[EMAIL PROTECTED]>, Paul
Johnson wrote:
>
> Kevin Pfeiffer said:
[...]
>> But what I can't figure out (and have tried several variants) is how to
>> get the count when using a variable (ala' from inside an eval). This is
>> the closet I got:
>>
>> my $sentence = "Here is my test sentence.\n";
>> my $letter = 'e';
>> my $count;
>>
>> eval {$count = $sentence =~ tr/$letter//};
>> die $@ if $@;
>>
>> print "The letter $letter appears $count times in the sentence...";
>>
>> It produces "The letter e appears 10 times..." but the answer should be
>> "6".
>> :-(
>
> You didn't follow the example - you changed the quotes for the eval.
>
> You need this:
>
> eval "\$count = \$sentence =~ tr/$letter//";
>
> or even better:
>
> $count = eval "\$sentence =~ tr/$letter//";
mumble, mumble... :-) I did try the example first, exactly has given in
perlop, but it didn't work. What I didn't try was the escape you use before
the string symbol.
> Read up on the two different types of eval, then you should be able to
> find out why you got 10.
Will do! It sounds like this might be a case of not having read far enough
(and I distantly remember having once read about two types of eval, but it
apparently hasn't sunken in, yet). Thanks for the tips.
-K
--
Kevin Pfeiffer
International University Bremen
--
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
Re: Count Function?
Kevin Pfeiffer said:
> Thanks to Sudarshan & Janek!
>
> I found this as suggested...
>
> # NOTE: (from perlop)
> # Because the transliteration table is built at com
> # pile time, neither the SEARCHLIST nor the REPLACE
> # MENTLIST are subjected to double quote interpola
> # tion. That means that if you want to use vari
> # ables, you must use an eval():
> #
> # eval "tr/$oldlist/$newlist/";
> # die $@ if $@;
> #
> # eval "tr/$oldlist/$newlist/, 1" or die $@;
>
> But what I can't figure out (and have tried several variants) is how to
> get the count when using a variable (ala' from inside an eval). This is the
> closet I got:
>
> my $sentence = "Here is my test sentence.\n";
> my $letter = 'e';
> my $count;
>
> eval {$count = $sentence =~ tr/$letter//};
> die $@ if $@;
>
> print "The letter $letter appears $count times in the sentence...";
>
> It produces "The letter e appears 10 times..." but the answer should be
> "6".
> :-(
You didn't follow the example - you changed the quotes for the eval.
You need this:
eval "\$count = \$sentence =~ tr/$letter//";
or even better:
$count = eval "\$sentence =~ tr/$letter//";
Read up on the two different types of eval, then you should be able to
find out why you got 10.
--
Paul Johnson - [EMAIL PROTECTED]
http://www.pjcj.net
--
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
Re: Count Function?
In article <[EMAIL PROTECTED]>, Sudarshan Raghavan
wrote:
> Nelson Ray wrote:
>
>>Does anyone know of any sort of a function or method in perl that returns
>>the number of times a search string exists in a scalar. Say, how many
>>"a's"
>>are there in this sentence? I am able to write it myself, but I was
>>wondering if Perl had an inherent function for cleaner operation. I tried
>>looking through the list of functions at www.perldoc.com without success.
>>Thanks a lot for any help.
>>
>
> tr/// is what you need, perldoc perlop
> Assuming your string is in $_, the number of a's will be
> my $acnt = tr/a//;
Thanks to Sudarshan & Janek!
I found this as suggested...
# NOTE: (from perlop)
# Because the transliteration table is built at com
# pile time, neither the SEARCHLIST nor the REPLACE
# MENTLIST are subjected to double quote interpola
# tion. That means that if you want to use vari
# ables, you must use an eval():
#
# eval "tr/$oldlist/$newlist/";
# die $@ if $@;
#
# eval "tr/$oldlist/$newlist/, 1" or die $@;
But what I can't figure out (and have tried several variants) is how to get
the count when using a variable (ala' from inside an eval). This is the
closet I got:
my $sentence = "Here is my test sentence.\n";
my $letter = 'e';
my $count;
eval {$count = $sentence =~ tr/$letter//};
die $@ if $@;
print "The letter $letter appears $count times in the sentence...";
It produces "The letter e appears 10 times..." but the answer should be "6".
:-(
--
Kevin Pfeiffer
International University Bremen
--
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
Re: Count Function?
Nelson Ray wrote at Thu, 26 Jun 2003 19:25:37 -0700: > Does anyone know of any sort of a function or method in perl that returns > the number of times a search string exists in a scalar. Say, how many "a's" > are there in this sentence? I am able to write it myself, but I was > wondering if Perl had an inherent function for cleaner operation. I tried > looking through the list of functions at www.perldoc.com without success. > Thanks a lot for any help. perldoc -q "How can I count the number of occurrences of a substring" Greetings, Janek -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
Re: Count Function?
Nelson Ray wrote: Does anyone know of any sort of a function or method in perl that returns the number of times a search string exists in a scalar. Say, how many "a's" are there in this sentence? I am able to write it myself, but I was wondering if Perl had an inherent function for cleaner operation. I tried looking through the list of functions at www.perldoc.com without success. Thanks a lot for any help. tr/// is what you need, perldoc perlop Assuming your string is in $_, the number of a's will be my $acnt = tr/a//; -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
Count Function?
Does anyone know of any sort of a function or method in perl that returns the number of times a search string exists in a scalar. Say, how many "a's" are there in this sentence? I am able to write it myself, but I was wondering if Perl had an inherent function for cleaner operation. I tried looking through the list of functions at www.perldoc.com without success. Thanks a lot for any help. -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
