[parser] adding support for expressions

src/ast.ml

@@ -2,12 +2,40 @@ type ident = string
 
 type location = Lexing.position * Lexing.position
 
+type const =
+  | CBool of bool
+  | CInt of int
+
+type monop =
+  | MOp_not
+  | MOp_minus
+
+type binop =
+  | BOp_add | BOp_sub | BOp_mul | BOp_div | BOp_mod
+  | BOp_and | BOp_or | BOp_eq | BOp_neq
+  | BOp_le | BOp_lt | BOp_ge | BOp_gt
+
+type triop =
+  | TOp_if
+
 type base_ty =
   | Tbool
   | Tint
 
-type p_pattern = string
-and p_expression = string
+type p_pattern =
+  | PP_var of ident
+  | PP_tuple of ident list
+
+type p_expression =
+  | PE_Const of const
+  | PE_Var of ident
+  | PE_MonOp of monop * p_expression
+  | PE_BinOp of binop * p_expression * p_expression
+  | PE_TriOp of triop * p_expression * p_expression * p_expression
+  | PE_app of ident * p_expression list
+  | PE_tuple of p_expression list
+  | PE_pre of p_expression
+  | PE_arrow of p_expression * p_expression
 
 type p_equation =
   { peq_patt: p_pattern;