• Subject: RE: Extract number from character field(Perl syntax) (wayy off topic)
  • From: Carl Friedberg <friedberg@xxxxxxxxxxx>
  • Date: Mon, 8 Nov 1999 14:06:43 -0500

I am a VMS system administrator and pretty good with networking, Windows NT,
various IBM os, and 40 years of experience (almost). I nearly choked when I
saw the one-liner, but Perl is famous for one liners.

This shows the good, the bad, and the ugly, in perl.

At first, I couldn't believe it would work, so I tried it (on nt, but it
doesn't matter with perl -- that's part of the good).

The perl regular expression engine apparently looks at this from right to
left:

/\d+/g

(the forward slash is a boundary character for match or substitute
expressions; anything between the two // is a regular expression, to be used
for matching or substituting)

the \d means a single character which is in the range 0-9
\d+ means one or more of those; thus the match operation is 1 or more
digits

/\d+/g means (the g stands for global) repeat the (match) operation as many
times as possible within the string.

$str =~ /\d+/g

This is a frequent expression seen in almost all perl programs. The =~
operator is the match operator; it says take the string on the left and see
what matches can be obtained with the regular expression on the right (you
may add an m between the tilde and the first forward slash, but it's not
required).

Now comes the part about Perl that I hate: perl magic

The entire expression is evaluated, and returns a result. If the result is a
list, the list will contain each of the matches. The expression

@num = ($str =~ /\d+/g) ;

tells perl to place each of the matches in the array num. Thus, the first
match will be in $num[0]; the second in $num[1]; etc. I would never have
figured this out without actually trying it, but, in perl, it does make
sense.

Perl has a steep learning curve (I've been doing it on and off for four
years now, and I still feel like a beginner). It's also available on almost
every platform, hardware and software, you could imagine: most IBM os,
almost every conceivable flavor of *n*x; VMS, nt; and MAC-os.

Carl Friedberg, carl@comets.com

-----Original Message-----
From: Joel Fritz [mailto:JFritz@sharperimage.com]
Sent: Monday, November 08, 1999 12:30 PM
To: 'MIDRANGE-L@midrange.com'
Subject: RE: Extract number from character field(Perl syntax)


No offense, Hans, but what does this say about the "typical Perl
programmer?"

> -----Original Message-----
> From: boldt@ca.ibm.com [mailto:boldt@ca.ibm.com]
> Sent: Monday, November 08, 1999 8:29 AM
> To: MIDRANGE-L@midrange.com
> Subject: RE: Extract number from character field
> 
> 
       /*          Snip                                */
> 
> 
> >>
> >>      @nums = $str =~ /\d+/g;
> >
       /*          Snip                                */
> 
> Believe it or not, that code is clear as a bell to a
> typical Perl programmer!
> 
> Cheers!  Hans
> 
> Hans Boldt, ILE RPG Development, IBM Toronto Lab, boldt@ca.ibm.com
> 
> 
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