teaching machines

CS 330 Lecture 8 – Regex Closeout

February 11, 2015 by Chris Johnson. Filed under cs330, lectures, spring 2015.

Agenda

• what ?s
• regex bingo
• a few more examples
  • links between images
  • double-spaces between sentences
  • finding repeats
  • ith field

TODO

Right now:

• You and a partner make a 4×4 grid of randomly generated strings. Include upper- and lowercase letters, numbers, whitespace, and punctuation. Keep the strings short. There’s no free space.

Before Friday:

• Familiarize yourself with grammars and ANTLR. Read Grammar: The Language of Languages and Getting Started with ANTLR. On a 1/4 sheet, write a little grammar to match a limited set of variable “declassignments”—variable declarations that also initialize their values. Allow for ints, strings, and booleans. Support only literals on the right-hand side ( int a = 5, boolean isYesterday = true, string name = "bingo"). Don’t worry about type checking. That belongs in the semantic analysis stage.

Code

links.rb

#!/usr/bin/env ruby

text = IO.read(ARGV[0])

text.gsub!(/<img.*?src="(.*?)".*?>/) do |tag|
  "<a href=\"#{$1}\">#{tag}</a>"
end

puts text

repeats.rb

#!/usr/bin/env ruby

text = "the the the quick quick brown brown brown fox fox jumps jumps jumps over over the the the the the the the the lazy lazy lazy dog dog dog dog"

# puts text.gsub(/(\w+)( \1)+/, '\1') 
puts text.gsub(/(\w+) (?=\1)/, '')

fixfix.rb

#!/usr/bin/env ruby

text = "A bee flew. Dr. Neeper sneezes. Ben went to St. John's. I didn't."

puts text.gsub(/(?<!Dr|St)\. /, '.  ')

Haiku