Question

How to generate sequence chars in Perl

Asked by: prasen

Hi,
I need to generate a sequence of alphabets (lower case a to z) in Perl 5.8
How to do this ?
ie. if one particular string (say MyNAME), exist more than once, then I need to append lower case "a" to the 1st string, then "b" to the 2nd string
it would be like -->
MyNAMEa
MyNAMEb
and so on
:
:
I need to generate the sequence of characters based on the nbr of count of existence of MyNAME

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Asked On
2006-09-20 at 02:42:28ID21995921
Tags

string

Topic

Perl Programming Language

Participating Experts
4
Points
50
Comments
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Answers

 

by: suhasbharadwajPosted on 2006-09-20 at 05:27:48ID: 17560052

Hi prasen,
why you want to keep count of MyNAME using "a to z",
instead you can use the counter for that.

suppose,

$str = "hello world hello nice to see you in EE";

@res = split('\s+',$str);
$count = 0;
$srch = "hello";

foreach $i (@res)
{
    if($i =~ /$srch/)
    {
        $count++;
    }
}

print $count; #gives the number of occurence of word "hello" in given string


Cheers!
Suhas

 

by: vi_srikanthPosted on 2006-09-20 at 05:42:42ID: 17560154

If u have the text in $text, try:

$counter='a';
$text=~s/(MyNAME)/$1 . $counter/ge;

 

by: vi_srikanthPosted on 2006-09-20 at 05:44:01ID: 17560167

or:

$counter=0;
$text=~s/(is)/$1 . chr($counter++ + 97)/ge;

 

by: prasenPosted on 2006-09-20 at 06:16:43ID: 17560424

My problem is ---
If MyNAME occurs more than once, then I need to make it unique by appending a to z at the end of it
Say, if  MyNAME occurs thrice, then
MyNAMEa
MyNAMEb
MyNAMEc

somehow, I could mage to get this as follows --

my $act="MyNAME";
my $count=3;
my $ii;
my @var=('a','b','c','d');   #### ------> need to make this dynamic or auto generated
for $ii (0..$count-1)
{
  print "cnt=$act"."$var[$ii]\n";

}

so, now my problem is how to generate the array from a to z without doing it as above
like, assigning a,b,c,.....
then I will use that array

 

by: Perl_DiverPosted on 2006-09-20 at 06:54:04ID: 17560704

You can increment alphas just like digits:

my $alpha = 'a';
my @array = ('MyNAME') x 100;
$_.=$alpha++ for @array;  
print "$_\n" for @array;

 

by: GnarOlakPosted on 2006-09-20 at 07:18:47ID: 17560924

Here's some code that does what you need.  I'll explain the regex in my next message:

use strict;

my $str = "hello world hello nice to see you in EE";

# get all the words
my @res = split('\s+',$str);
my %h;

# store some information about them
foreach my $word (@res)
{
      # test that we didn't get some puctuation
      if ($word =~ /\w+/)
      {
            # how many of them?
            $h{$word}{count}++;
            
            # if there are more than one then we will add the salt
            $h{$word}{salt} = ($h{$word}{count} > 1 ? 'a' : '');
      }
}

# here's the tricky bit:
$str =~ s/(\b\w+\b)/$h{$1}{count} < 2 ? $1 : $1.$h{$1}{salt}++/ge;

print $str, "\n";
__END__

prints:
helloa world hellob nice to see you in EE

 

by: GnarOlakPosted on 2006-09-20 at 07:27:41ID: 17561011

Here's the line that does the work:

$str =~ s/(\b\w+\b)/$h{$1}{count} < 2 ? $1 : $1.$h{$1}{salt}++/ge;

The first part should be fairly easy to understand:
$str =~ s/(\b\w+\b)/

Match characters on word boundaries

This part:

/$h{$1}{count} < 2 ? $1 : $1.$h{$1}{salt}++/ge;

might need some explanation.

$1 will hold the word that has been matched
$h{$1}{count} will be the count of that words occurances within the text.
Then that is tested to see if it is less than 2.  I like to use that instead of '== 1' just in case...

If the count of that words occurances is less than two the the first part after the ? is what is substituted.  In this case it is just $1 which means that words that occur only once will be substituted for themself.  If the count is two or more then the result of the ? test will be the part following the : which is:

$1.$h{$1}{salt}++

In this case the substitution is the word followed by the salt value for that word, $h{$1}{salt}.  Then the salt value is incremented so that a becomes b and b becomes c, etc.

The last bit, /ge, says to apply the expression globally to the string and the e says to treat the second part of the substitution as an expression that must be evaluated.

And a footnote:  It really wasn't necessary to test the count of the words in the first loop before creating the salt value.  Since the test is made when the words are being processed by the regex, had a word with a count of one had a salt value it simply would have been ignored.

So this line:

$h{$word}{salt} = ($h{$word}{count} > 1 ? 'a' : '');

can actually be:

$h{$word}{salt} = 'a';

and the code will work just as well.

20120131-EE-VQP-002

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