Type checking for miniFun, adding some tests
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elvis
138
lib/miniFun.ml
138
lib/miniFun.ml
@ -2,11 +2,16 @@ type variable = string
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module VariableMap = Map.Make(String)
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type ftype =
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IntegerType
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| BooleanType
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| FunctionType of ftype list * ftype
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type t_exp =
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Integer of int
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| Boolean of bool
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| Variable of variable
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| Function of variable list * t_exp
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| Function of variable list * ftype * t_exp
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| Application of t_exp * t_exp list
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| Plus of t_exp * t_exp
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| Minus of t_exp * t_exp
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@ -26,7 +31,7 @@ type t_exp =
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| CmpGreaterEq of t_exp * t_exp
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| IfThenElse of t_exp * t_exp * t_exp
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| LetIn of variable * t_exp * t_exp
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| LetFun of variable * variable list * t_exp * t_exp
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| LetFun of variable * variable list * ftype * t_exp * t_exp
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type permittedValues =
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IntegerPermitted of int
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@ -47,6 +52,7 @@ exception AbsentAssignment of string
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exception WrongType of string
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exception DivisionByZero of string
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exception WrongAriety of string
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exception WrongTypeSpecification of string
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module Utility = Utility;;
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@ -63,7 +69,7 @@ let rec evaluate (mem: memory) (command: t_exp) =
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" is not defined."))
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| Some a -> a
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)
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| Function (xs, f) ->
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| Function (xs, _, f) ->
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(FunctionPermitted
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{inputList = xs;
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body = f;
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@ -335,7 +341,7 @@ let rec evaluate (mem: memory) (command: t_exp) =
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let evalxval = evaluate mem xval in
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let mem2 = {assignments = VariableMap.add x evalxval mem.assignments} in
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evaluate mem2 rest
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| LetFun (f, xs, fbody, rest) ->
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| LetFun (f, xs, _, fbody, rest) ->
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let mem2 = {
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assignments =
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VariableMap.add
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@ -356,3 +362,127 @@ let reduce (program: t_exp) (iin : int) =
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match (evaluate mem program') with
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IntegerPermitted a -> a
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| _ -> raise (WrongType ("Main function doesn't return an integer"))
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let rec evaluate_type (program: t_exp) context =
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match program with
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Integer _ -> IntegerType
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| Boolean _ -> BooleanType
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| Variable x -> (match VariableMap.find_opt x context with
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None -> raise (AbsentAssignment ("The variable " ^ x ^ " is not defined."))
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| Some t -> t)
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| Function (xs, typef, fbody) -> (
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match typef with
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FunctionType (tin, tout) -> (
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if List.length xs != List.length tin then
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raise (WrongTypeSpecification "Type specification for function has wrong ariety.")
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else
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let context1 = List.fold_left2 (fun acc x t -> VariableMap.add x t acc) context xs tin in
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match (evaluate_type fbody context1 = tout) with
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(false) -> raise (WrongTypeSpecification "Function does not return specified type.")
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| (true) -> typef
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)
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| _ -> raise (WrongTypeSpecification "Specification of function is not a function type.")
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)
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| Application (f, xs) -> (
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match evaluate_type f context with
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FunctionType (tin, tout) -> (
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let rec helper params typeparams =
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match (params, typeparams) with
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([], _) -> typeparams
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| (_, []) -> raise (WrongAriety ("Function application has arity " ^
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(List.length tin |> string_of_int) ^
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", but was applied to " ^
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(List.length xs |> string_of_int) ^
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" parameters"))
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| (p::tlparams, v::tltypeparams) ->
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if evaluate_type p context = v then
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helper tlparams tltypeparams
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else
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raise (WrongType "Argument with wrong type.")
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in
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match helper xs tin with
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[] -> tout
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| t -> FunctionType (t, tout)
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)
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| _ -> raise (WrongType "Applying to a non function type")
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)
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| Plus (x, y)
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| Minus (x, y)
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| Times (x, y)
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| Division (x, y)
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| Modulo (x, y)
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| Power (x, y) -> (
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match (evaluate_type x context, evaluate_type y context) with
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| (IntegerType, IntegerType) -> IntegerType
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| (IntegerType, _) -> raise (WrongType "Second term is not an integer.")
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| (_, _) -> raise (WrongType "First term is not an integer.")
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)
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| PowerMod (x, y, z) -> (
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match (evaluate_type x context, evaluate_type y context, evaluate_type z context) with
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| (IntegerType, IntegerType, IntegerType) -> IntegerType
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| (IntegerType, IntegerType, _) -> raise (WrongType "Third term is not an integer.")
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| (IntegerType, _, _) -> raise (WrongType "Second term is not an integer.")
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| (_, _, _) -> raise (WrongType "First term is not an integer.")
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)
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| Rand (x) -> (
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match (evaluate_type x context) with
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| (IntegerType) -> IntegerType
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| (_) -> raise (WrongType "Term is not an integer.")
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)
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| BAnd (x, y)
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| BOr (x, y) -> (
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match (evaluate_type x context, evaluate_type y context) with
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| (BooleanType, BooleanType) -> BooleanType
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| (BooleanType, _) -> raise (WrongType "Second term is not a boolean.")
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| (_, _) -> raise (WrongType "First term is not a boolean.")
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)
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| BNot (x) -> (
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match (evaluate_type x context) with
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| (BooleanType) -> BooleanType
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| (_) -> raise (WrongType "Term is not a boolean.")
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)
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| Cmp (x, y)
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| CmpLess (x, y)
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| CmpLessEq (x, y)
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| CmpGreater (x, y)
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| CmpGreaterEq (x, y) -> (
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match (evaluate_type x context, evaluate_type y context) with
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| (IntegerType, IntegerType) -> BooleanType
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| (IntegerType, _) -> raise (WrongType "Second term is not an integer.")
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| (_, _) -> raise (WrongType "First term is not an integer.")
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)
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| IfThenElse (guard, if_exp, else_exp) -> (
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match (evaluate_type guard context, evaluate_type if_exp context, evaluate_type else_exp context) with
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(BooleanType, t1, t2) -> (
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if t1 = t2 then
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t1
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else
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raise (WrongType "If branches do not have the same type.")
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)
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| (_, _, _) -> raise (WrongType "If guard is not a boolean.")
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)
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| LetIn (x, xval, rest) ->
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let typex = evaluate_type xval context in
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evaluate_type rest (VariableMap.add x typex context)
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| LetFun (f, xs, typef, fbody, rest) ->
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match typef with
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FunctionType (tin, tout) -> (
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if List.length xs != List.length tin then
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raise (WrongAriety "Type specification for function has wrong ariety.")
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else
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let context1 = VariableMap.add f typef context in
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let context2 = List.fold_left2 (fun acc x t -> VariableMap.add x t acc) context1 xs tin in
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match (evaluate_type fbody context2 = tout, evaluate_type rest context1) with
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(false, _) -> raise (WrongTypeSpecification "Function does not return specified type."
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)
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| (true, t) -> t
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)
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| _ -> raise (WrongTypeSpecification "Specification of function is not a function type.")
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let typecheck (program: t_exp) =
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match evaluate_type program VariableMap.empty with
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FunctionType ([IntegerType], IntegerType) -> true
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| _ -> raise (WrongType "Program is not a function from int to int.")
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