teaching machines

CS 330 Lecture 7 – Regex Cont’d

February 9, 2015 by Chris Johnson. Filed under cs330, lectures, spring 2015.

Agenda

• what ?s
• what does this do?
• substitution
• capturing
• lookaround assertions

TODO

• 1/4 sheet: Try your hand at Regex Golf. Report some of your regices and your score.

What Does This Do?

1. #!/usr/bin/env ruby
   
   Dir.glob('*.html?').each do |f|
     File.delete(f)
   end

2. #!/usr/bin/env ruby
   
   text = IO.read(ARGV[0]);
   text.scan(/a\s*[aeiou]/) do |match|
     puts match
   end

3. #!/usr/bin/env ruby
   
   text = IO.read(ARGV[0])
   puts text.scan(/"[^"]*"/)

4. #!/usr/bin/env ruby
   
   puts IO.read(ARGV[0]).scan(/\bcos\b)

Code

arithmetic.txt

Day 1: the number of bunnies was {{ 5 }}.

Day 2: the number of bunnies was {{ 5 * 2 }}.

Day 3: the number of bunnies was {{ 5 ** 40 }}.

calc.rb

#!/usr/bin/env ruby

raw = IO.read(ARGV[0])

cooked = raw.gsub(/\{\{(.*?)\}\}/) do |match|
  # puts match 
  # puts $1 
  eval($1)
end

puts cooked

music.rb

#!/usr/bin/env ruby

notes = "A B C C# Db A B G Ab Bb C# Db G#"

cooked = notes.gsub(/A(?!b|#)/, 'G')

puts notes
puts cooked

Haiku