49 lines
1.6 KiB
Plaintext
49 lines
1.6 KiB
Plaintext
(* Useful for resource cleanup (such as filehandles) *)
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let try_finally x f g =
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try let res = f x in g x; res
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with e -> g x; raise e
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(* Substitute string 'b' for first occurance of regexp 'a' in 's';
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* Raise Not_found if there was no occurance of 'a'. *)
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let subst a b s =
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ignore (Str.search_forward a s 0); (* to generate Not_found *)
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Str.replace_first a b s
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let parse_rules cin =
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let open Str in
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let rule = regexp "\\(.+\\)[ \t]+->[ \t]+\\(.*\\)" in
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let leader s c = String.length s > 0 && s.[0] = c in
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let parse_b s = if leader s '.' then (string_after s 1,true) else (s,false) in
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let rec parse_line rules =
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try
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let s = input_line cin in
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if leader s '#' then parse_line rules
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else if string_match rule s 0 then
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let a = regexp_string (matched_group 1 s) in
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let b,terminate = parse_b (matched_group 2 s) in
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parse_line ((a,b,terminate)::rules)
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else failwith ("parse error: "^s)
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with End_of_file -> rules
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in List.rev (parse_line [])
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let rec run rules text =
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let rec apply s = function
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| [] -> s
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| (a,b,term)::next ->
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try
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let s' = subst a b s in
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if term then s' else run rules s'
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with Not_found -> apply s next
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in apply text rules
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let _ =
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if Array.length Sys.argv <> 2 then
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print_endline "Expecting one argument: a filename where rules can be found."
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else
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let rules = try_finally (open_in Sys.argv.(1)) parse_rules close_in in
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(* Translate lines read from stdin, until EOF *)
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let rec translate () =
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print_endline (run rules (input_line stdin));
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translate ()
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in try translate () with End_of_file -> ()
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