1 files changed, 48 insertions, 0 deletions
diff --git a/users/wpcarro/scratch/compiler/parser.ml b/users/wpcarro/scratch/compiler/parser.ml
new file mode 100644
index 000000000000..75cbe04a3f72
--- /dev/null
+++ b/users/wpcarro/scratch/compiler/parser.ml
@@ -0,0 +1,48 @@
+(*******************************************************************************
+ * Defines a generic parser class.
+ ******************************************************************************)
+
+exception ParseError of string
+
+type token = string
+type state = { i : int; tokens : token array }
+
+let get (i : int) (xs : 'a array) : 'a option =
+  if i >= Array.length xs then None else Some xs.(i)
+
+class parser (tokens : token array) =
+  object (self)
+    val mutable tokens : token array = tokens
+    val mutable i = ref 0
+    method print_state = Printf.sprintf "{ i = %d; }" !i
+    method advance = i := !i + 1
+    method prev : token option = get (!i - 1) tokens
+    method curr : token option = get !i tokens
+    method next : token option = get (!i + 1) tokens
+
+    method consume : token option =
+      match self#curr with
+      | None -> None
+      | Some x as res ->
+          self#advance;
+          res
+
+    method expect (x : token) =
+      match self#curr with
+      | Some y when x = y -> self#advance
+      | _ -> raise (ParseError (Printf.sprintf "Expected %s" x))
+
+    method matches (x : token) : bool =
+      match self#curr with
+      | None -> false
+      | Some y ->
+          if x = y then
+            begin
+              self#advance;
+              true
+            end
+          else false
+
+    method exhausted : bool = !i >= Array.length tokens
+    method state : state = { i = !i; tokens }
+  end