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Can You Do the Regular Expression Crossword?
mikejuk writes "Programmers often say that regular expressions are fun ... but now they can be a whole lot of fun in a completely new way. Want to try your hand at a regular expression crossword? The idea is simple enough — create a crossword style puzzle with regular expressions are the 'clues.' In case you don't know what a regular expression is — it is a way of specifying what characters are allowed using wild-card characters and more. For example a dot matches any single character, an * any number of characters and so on. The regular expression crossword is more a sort of Sudoku puzzle than crossword however because the clues determine the pattern that the entries in a row have to satisfy. It also has to use a hexagonal grid to provide three regular expressions to control each entry. This particular regular expression crossword(pdf) was part of this year's MIT Mystery Hunt. This annual event is crammed with a collection of very difficult problems and the regular expression crossword, created by Dan Gulotta from an idea by Palmer Mebane, was just a small part of the whole — and yes there is a solution."
The only thing difficult about the puzzle is the format in which it is presented. How many people have printers? Of those, how many have working printers? And, of those, how many also have paper?
No need to print out the puzzle, somebody made an interactive version:
http://twoevils.net/cross-regex.html
Randall should draw a comic about obligatory xkcd references.