in reply to Rosetta PGA-TRAM
let explode str = let rec aux pos acc = if pos < 0 then acc else aux (pred pos) (str.[pos] :: acc) in aux ((String.length str)-1)  let d2a = function | 'M' -> 1000 | 'D' -> 500 | 'C' -> 100 | 'L' -> 50 | 'X' -> 10 | 'V' -> 5 | 'I' -> 1 | _ -> failwith "Incorrect character" let r2d str = List.fold_left (fun acc x -> let x' = d2a x in acc + x' - acc mod +x' * 2) 0 (explode (String.uppercase str));;
- explode just converts a string into a list of its characters. The future standard library for OCaml, named Batteries included will include such a function by default.
- The functional nature of OCaml allows a natural implementation of the algorithm