38 lines
1.4 KiB
OCaml
38 lines
1.4 KiB
OCaml
module type S = sig
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include Syntax.S
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type t
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val parse: Cursor.t -> t -> t
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end
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module type Sub_parsers = sig
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type t
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val subparsers: (module S with type t = t) array
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end
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let at s e cur ch = if s cur ch then Cursor.find_end e cur else None
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let apply_default (type a) (module P: S with type t = a) (acc: a) cursor_default cursor =
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if cursor_default = cursor then acc
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else P.parse (Cursor.sub ~right:(cursor.Cursor.pos) cursor_default) acc
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let rec branch: type a. ?idx:int -> a -> Cursor.t -> Cursor.t -> (module S with type t = a) array -> (a * Cursor.t) =
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fun ?idx:(i=1) acc cursor_default cursor syntaxes ->
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if Cursor.overran cursor then (apply_default syntaxes.(0) acc cursor_default cursor), cursor
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else
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try let (module P: S with type t = a) = syntaxes.(i) in
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(match at P.s P.e cursor (Cursor.char cursor) with
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| Some right ->
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let acc = apply_default syntaxes.(0) acc cursor_default cursor in
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let acc = P.parse (Cursor.sub ~right cursor) acc in
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let cursor = Cursor.sub ~left:right cursor in
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branch acc cursor cursor syntaxes
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| None | exception Invalid_argument _ -> branch ~idx:(i+1) acc cursor_default cursor syntaxes)
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with Invalid_argument _ ->
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branch acc cursor_default (Cursor.next_char cursor) syntaxes
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let rec parse subsyntaxes cursor acc =
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if Cursor.overran cursor then acc
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else
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let acc, cursor = branch acc cursor cursor subsyntaxes in
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parse subsyntaxes cursor acc
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