57 lines
1.6 KiB
OCaml
57 lines
1.6 KiB
OCaml
(* Variables are strings. *)
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type variable =
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string
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(* Every [let] binding is marked recursive or nonrecursive. *)
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and recursive =
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| Recursive
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| NonRecursive
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(* The four standard integer arithmetic operations are supported. *)
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and binop =
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| OpAdd
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| OpSub
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| OpMul
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| OpDiv
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(* This language is the untyped lambda-calculus, extended with possibly
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recursive [let] bindings, integer literals (that is, constants), integer
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arithmetic operations, and the primitive operation [print], which prints an
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integer value and returns it. *)
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and term_ =
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| Var of variable
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| Lam of variable * term
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| App of term * term
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| Lit of int
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| BinOp of term * binop * term
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| Print of term
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| Let of recursive * variable * term * term
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| IfZero of term * term * term
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(* Every abstract syntax tree node of type [term] is annotated with a place,
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that is, a position in the source code. This allows us to produce a good
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error message when a problem is detected. *)
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and term =
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term_ placed
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(* A value of type ['a placed] can be thought of as a value of type ['a]
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decorated with a place. *)
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and 'a placed = {
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place: Error.place;
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value: 'a
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}
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(* The following annotation requests the automatic generation of a [show_]
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function for each of the types defined above. For instance, the function
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[show_term], of type [term -> string], converts a term to a string. These
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functions can be useful during debugging. Running with [--debug] causes
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every intermediate abstract syntax tree to be displayed in this way. *)
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[@@deriving show { with_path = false }]
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