From: Jan Svitok <jan.svitok@...>
Date: 2006-08-12T18:09:41+09:00
Subject: Re: Regexp Parsing -- What's the right way?

On 8/12/06, skelastic@gmail.com <skelastic@gmail.com> wrote:
> Greetings,
>
> I'm trying to parse the following line:
> ...

Hi,

although in this case I'd prefer the array.split solution here's how
it can be done in case you really need regex:
These are incremental versions of the regex, and a test to check them.
Save to file and enjoy!

Jano

#!/usr/bin/ruby
require 'test/unit'

DATA = "00608 P 135 001 LEC Tu 2-5P 210 WHEELER IT and Society 3 LAGUERRE"

REGEX1 = /(\d{5}).(\D\s\w{2,4}).(\d{1,4}\s\D{3}).(\D{1,4}\s\d+).*(\d{1,4}\s\D{1,9}).(\w+).*(\d?).*(\w{1,14}).*/

# add /x and # comments,
REGEX2 = /
	(\d{5}).		# control
	(\D\s\w{2,4}).		# course
	(\d{1,4}\s\D{3}).	# section
	(\D{1,4}\s\d+).*	# day-hour
	(\d{1,4}\s\D{1,9}).	# room
	(\w+).*			# course-name
	(\d?).*			# credits
	(\w{1,14}).*		# professor
/x

# now we'll fix the day-hour: add -\d[AP] - that will match a slash,
# a digit and either 'A' or 'P'
# and fix for the room: \D{1,9} replace with \w+
REGEX3 = /
	(\d{5}).		# control
	(\D\s\w{2,4}).		# course
	(\d{1,4}\s\D{3}).	# section
	(\D{1,4}\s\d+-\d[AP]).	# day-hour
	(\d{1,4}\s\w+).		# room
	(\w+).*			# course-name
	(\d?).*			# credits
	(\w{1,14}).* 		# professor
/x

# To fix course name, the previous tricks aren't enough --
# there are many words, with different length. So what we'll do?
# We'll parse the things at the end: credits and professor
#
# To see the results, temporarily comment out the lines
# that checks the course name and credits in the test
# and run it with REGEX3.
#
# To fix the professor, we'll say that it's tha last word on the line:
# notice the \s+ before the professor group - there has to be something
# fixed that separates the name from the rest - .* won't do it.
REGEX4 = /
	(\d{5}).		# control
	(\D\s\w{2,4}).		# course
	(\d{1,4}\s\D{3}).	# section
	(\D{1,4}\s\d+-\d[AP]).	# day-hour
	(\d{1,4}\s\w+).		# room
	(\w+).*			# course-name
	(\d?)\s+		# credits
	(\w+)\s*$ 		# professor
/x

# Now we can try the rest two pieces: uncomment credits and
# we'll see that they are already ok, so uncomment course name as well.
#
# Only the first word appears. So we'll move .* inside the parentheses
# and add a separating \s+
#
# Finally some small touches:
# replace separating . with \s+
REGEX5 = /
	(\d{5})\s+		# control
	(\D\s\w{2,4})\s+	# course
	(\d{1,4}\s\D{3})\s+	# section
	(\D{1,4}\s\d+-\d[AP])\s+# day-hour
	(\d{1,4}\s\w+)\s+	# room
	(.*)\s+			# course-name
	(\d+)\s+		# credits
	(\w+)\s*$ 		# professor
/x

class TestRegex < Test::Unit::TestCase
	def test_regex
		assert DATA =~ REGEX1  # <--- change number here
		assert_equal "00608", $1
		assert_equal "P 135", $2
		assert_equal "001 LEC", $3
		assert_equal "Tu 2-5P", $4
		assert_equal "210 WHEELER", $5
		assert_equal "IT and Society", $6
		assert_equal "3", $7
		assert_equal "LAGUERRE", $8
	end
end