Compsci 06, Spring 2012, Regex FUN, April 3

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This downloadable tool will help as you experiment with regular expressions.

  1. The expression ate$ matches 540 words and the expression ^s.*ate$ matches 30 words. What are the differences and similarities (written description) between the matches of these two expressions?
  2. The expression ^p.[o|a].e$ matches 14 words, what features do these words have in common?
  3. The regular expression (....)\1 has one match, the word beriberi. A small change to the regex, (....).\1 generates two matches: bandstands and hodgepodge. Explain why beriberi doesn't match the second expression and why the two words that match the second expression match it and not the first regex.
  4. The regex (....).*\1 has 13 matches: 
    atherosclerosis 
bandstands 
beriberi 
hodgepodge 
kinnickinnic 
knickerbocker 
knickerbockers 
lightweight 
misunderstander 
misunderstanders 
nationalization 
rationalization 
rationalizations
    Explain why atherosclerosis matches. Circle the five of these that also match (.....).*\1 (there's one more dot).

  5. Find all the words that have all the vowels a,e,i,o,u and in that order.
  6. Find the number of words that contain either "spis" or "spas" in them. Ideally you'll do this using one regex. What is the regex?
  7. Find all seven letter palindromes using one regex.