draft of data structure for the AST

Types.hs

+module Types where
+type Program = (InputSymbols,Output)
+
+type SymbolName = String
+type InputSymbols = [String] -- .in section
+type Output = [OutputLine] -- .out section
+
+data OutputLine = Let SymbolName Expr | Expr -- Expr always a function call for a set function, but not enforced by AST.
+
+data PredefFunc = XProduct | XXProduct | IsEqual | IsNotEqual | Add --operators
+    | Map | Filter
+    | RecordIndex -- [] operator
+    | IsEmpty | NotEmpty -- string functions
+
+
+--n.b. these definitions do not enforce type checking! The use of any function or operator will be associated with a FuncCall.
+--Therefore, it is possible to have ASTs with ridiculous things where e.g. a XX product is applied to and int and a String, or a function call has an Int as a function!
+--These issues will be checked via the type checker after the AST has been built.
+
+data Expr = FuncCall {func::Expr, inputSets::[Expr], args::[Expr]} -- args: function to call, input sets, extra argument. Applicable for all kinds of functions: the set functions e.g. filter, map or simple functions or even the operators e.g. ==, /= ! We don't define separate expr for each operator
+    | FuncDef {name::SymbolName, inputSetNames::[SymbolName], argsNames::[SymbolName], body::Expr} -- function definition
+    | If Expr Expr Expr
+    | Set [Expr]
+    | Tuple [Expr]
+    | Record [Expr]
+    | PredefFunc PredefFunc
+    | Var SymbolName
+    | Int Int
+    | String String
+    | Boolean Bool
+
+data Parameter = NamedParam SymbolName | TupleMatch [SymbolName]
\ No newline at end of file