Execute a Markov algorithm: Difference between revisions

(* At their simplest, modules can function like namespaces... though they're much more. *)

module Markov = struct

let parse_rules cin =

let open Str in

let rule = regexp "\\(.+\\)[ \t]+->[ \t]+\\(.*\\)" in

let leader s c = String.length s > 0 && s.[0] = c in

let parse_b s = if leader s '.' then (string_after s 1,true) else (s,false) in

let rec parse_line rules =

try

let s = input_line cin in

if leader s '#' then parse_line rules

else if string_match rule s 0 then

let a = regexp_string (matched_group 1 s) in

let b,terminate = parse_b (matched_group 2 s) in

parse_line ((a,b,terminate)::rules)

else failwith ("parse error: "^s)

with End_of_file -> rules

in List.rev (parse_line [])

let rec run rules text =

let rec apply s = function

| [] -> s

| (a,b,term)::next ->

try

let s' = subst a b s in

if term then s' else run rules s'

with Not_found -> apply s next

in apply text rules

end

let rules = try_finally (open_in Sys.argv.(1)) Markov.parse_rules close_in in

print_endline (Markov.run rules (input_line stdin));