Hello:
I'm trying to work through the "Learning Perl" Llama book, but I'm a bit
stumped on one of the regex exercises (ch 8.6 #3). The solution at the back of
the book doesn't work if you don't presume anything for input.
Anyway, what the book asks is to write a regular expression that will parse a
file for scalar variables. I've found its not so easy, particularly if you
don't want to presume anything on the input, e.g.:
# Given a file, e.g.: ~/filetoparse.txt (exclude comments)
$0 # "shouldn't match special variables like $0"
$the1stScalar # OK
$$notaScalar # improper syntax
$the2ndScalar . # preceeding or trailingspaces or tabs OK
thisis$notaScalar # improper syntax
$the3rdScaler = $the4thScalar # multiple variables OK
$thisIsNOT@scalar $the5thScaler the end. # invalid character (@)
# The output I'm trying to get to:
$the1stScalar
$the2ndScalar
$the3rdScaler
$the4thScalar
$the5thScaler
Anyway, I've racked my brain for days, and I still can't get very close. A key
issue seems to be matching a variable at the beginning of the line (^ anchor?)
OR preceded by \s character. This is the code/regex snippets I"m using to test
my attempts, and few of the examples I've tried (commented out:
#!/usr/usperl -w
### Yes its ugly, but it all works for my purposes here
use strict;while(<>){chomp;if(
### Uncomment regex to test
# /\$([\w])+/
# /\$[a-zA-Z_]+[a-zA-Z_\d]*/
# /\s\$[a-zA-Z_]+[a-zA-Z_\d]*/
# /( |\t|^\w)\${1}[a-zA-Z_]+[a-zA-Z_\d]*\b/
/^\$[A-Za-z_]\w*$/ # example from back of book doesn't work well
###
){print "$&\t\t$`$&$'\n";}}
Maybe somebody has some ideas I haven't thought of? I could probably spring
for a Carl's Jr "$6 dollar burger & Lord of the Rings "The Two Towers" ticket
(all via-Paypal) if anyone has a solid solution.
Thanks,
Lance
-----------------------------------------------------------------------------
#!/usr/bin/perl
print "Lance Murray, Information and Communications Systems\n", # department
"The Church of Jesus Christ of Latter-Day Saints\n", # employer and religion
"(801) 240-6583, murraylk\@ldschurch.org\n\n", # work phone number and email
"\"Better to do a little well than a lot poorly\" (Socrates)\n"; # philosophy
@P=split//,".URRUU\c8R";@d=split//,"\nrekcah xinU / lreP rehtona tsuJ";sub p{
@p{"r$p","u$p"}=(P,P);pipe"r$p","u$p";++$p;($q*=2)+=$f=!fork;map{$P=$P[$f^ord
($p{$_})&6];$p{$_}=/ ^$P/ix?$P:close$_}keys%p}p;p;p;p;p;map{$p{$_}=~/^[P.]/&&
close$_}%p;wait until$?;map{/^r/&&<$_>}%p;$_=$d[$q];sleep rand(2)if/\S/;print
------------------------------------------------------------------------------
This message may contain confidential information, and is intended only for the use of
the individual(s) to whom it is addressed.
==============================================================================
BEGIN:VCARD
VERSION:2.1
X-GWTYPE:USER
FN:Lance Murray
N:Murray;Lance
TITLE:Network Engineer
TEL;WORK:+1-801-240-6583
TEL;PREF;FAX:+1-801-240-5237
ORG:;Info. and Comm. Sys.
ADR;DOM;WORK;PARCEL;POSTAL:;CCC 216A-16;125 North State;Salt Lake City;Utah;84103
LABEL;DOM;WORK;PARCEL;POSTAL;ENCODING=QUOTED-PRINTABLE:Lance Murray=0A=
CCC 216A-16=0A=
125 North State=0A=
Salt Lake City, Utah 84103
EMAIL;WORK;PREF;NGW:[EMAIL PROTECTED]
END:VCARD
--
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
