Monday, March 31, 2008
Finger Exercises
Wow. Three months, no update. Hm.
I've been working on a bunch of little projects recently that individually don't amount to much, yet. I should have something to post about that soon.
In the mean time, here is a cute little problem (via Uri to the fun with Perl list):
What is an easy way to get all possible combinations of Y/N of length 5? (i.e., "YYYYY", "YYYYN", etc.)
Coming up with a solution to this exact problem seemed to cry out for a list comprehension:
[[a,b,c,d,e] | let l <- "YN",
a <- l, b <- l, c <- l, d <- l, e <- l]
but as soon as I wrote that, I saw how unsatisfactory it was. A better solution would produce all possible combinations of Y and N for a list of any integer n> 0:
yn i = (iterate f [""]) !! i
where f l = map ('Y':) l ++ map ('N':) l
This problem itself isn't very interesting, but it's good to have little diversions like this when you want to take a break while the coffee is steeping, waiting for the Guinness to settle, or whatnot. (Something that's more than a function from the Prelude, but less involved than something from Project Euler.)
Do you have any cute little "finger exercise" problems like these? I'd love to hear about them!