Over on his blog, Andrei Formiga has a series of post on implementing ROT13 in F# and Haskell.
I like is implementation using library functions that don’t yet exist in F#, such as drop and zip. Here is the implementation itself, stripped of the extra library functions he had to implement, for the original see the above links.
let rot13 s = let letters = ['a' .. 'z'] let transp = zip letters ((drop 13 letters) @ (take 13 letters)) let rotchar c = List.assoc c transp strmap rotchar s
The clever bit of...