words with duplicate letters
Some words have duplicate letters ("book"—two o's—or "that"—two t's). Many don't.
Your task is to write a predicate that returns
true if the string contains any words with duplicate letters.
(duplicate-letter? "Hello, my friend!") =>
true (because "hello" has two l's)
(duplicate-letter? "Hey friend!") =>
false (because no words have duplicates)
Have fun with this one! Try out different ways to implement it.
Thanks to to this site for the challenge idea!