open Pcaml;;

EXTEND
  GLOBAL: expr;

  expr: 
    [ [ "map"; list = expr; "with"; OPT "|"; clauses = LIST1 clause SEP "|" ->
	  <:expr< List.map (fun [ $list:clauses$ ]) $list$ >> ]

    | [ "iterate"; list = expr; "with"; OPT "|"; clauses = LIST1 clause SEP "|" ->
	  <:expr< List.iter (fun [ $list:clauses$ ]) $list$ >> ]
	
    | [ "foldr"; list = expr; "from"; initval = expr; "with"; OPT "|"; 
	clauses = LIST1 clause SEP "|" ->
	  <:expr< List.fold_right (fun a b -> 
				     match (a, b) with [ $list:clauses$ ]) 
	                           $list$ $initval$ >> ]

    | [ "foldl"; list = expr; "from"; initval = expr; "with"; OPT "|"; 
	clauses = LIST1 clause SEP "|" ->
	  <:expr< List.fold_left (fun a b -> 
				     match (a, b) with [ $list:clauses$ ]) 
	                           $initval$ $list$ >> ]
    ];

  clause:
    [[ p = patt; w = OPT when_expr; "->"; e = expr -> (p, w, e)]];

  when_expr:
    [[ "when"; e = expr -> e ]];
END;;