--- /dev/null
+(*===---------------------------------------------------------------------===
+ * Parser
+ *===---------------------------------------------------------------------===*)
+
+(* binop_precedence - This holds the precedence for each binary operator that is
+ * defined *)
+let binop_precedence:(char, int) Hashtbl.t = Hashtbl.create 10
+
+(* precedence - Get the precedence of the pending binary operator token. *)
+let precedence c = try Hashtbl.find binop_precedence c with Not_found -> -1
+
+(* primary
+ * ::= identifier
+ * ::= numberexpr
+ * ::= parenexpr
+ * ::= ifexpr
+ * ::= forexpr *)
+let rec parse_primary = parser
+ (* numberexpr ::= number *)
+ | [< 'Token.Number n >] -> Ast.Number n
+
+ (* parenexpr ::= '(' expression ')' *)
+ | [< 'Token.Kwd '('; e=parse_expr; 'Token.Kwd ')' ?? "expected ')'" >] -> e
+
+ (* identifierexpr
+ * ::= identifier
+ * ::= identifier '(' argumentexpr ')' *)
+ | [< 'Token.Ident id; stream >] ->
+ let rec parse_args accumulator = parser
+ | [< e=parse_expr; stream >] ->
+ begin parser
+ | [< 'Token.Kwd ','; e=parse_args (e :: accumulator) >] -> e
+ | [< >] -> e :: accumulator
+ end stream
+ | [< >] -> accumulator
+ in
+ let rec parse_ident id = parser
+ (* Call. *)
+ | [< 'Token.Kwd '(';
+ args=parse_args [];
+ 'Token.Kwd ')' ?? "expected ')'">] ->
+ Ast.Call (id, Array.of_list (List.rev args))
+
+ (* Simple variable ref. *)
+ | [< >] -> Ast.Variable id
+ in
+ parse_ident id stream
+
+ (* ifexpr ::= 'if' expr 'then' expr 'else' expr *)
+ | [< 'Token.If; c=parse_expr;
+ 'Token.Then ?? "expected 'then'"; t=parse_expr;
+ 'Token.Else ?? "expected 'else'"; e=parse_expr >] ->
+ Ast.If (c, t, e)
+
+ (* forexpr
+ ::= 'for' identifier '=' expr ',' expr (',' expr)? 'in' expression *)
+ | [< 'Token.For;
+ 'Token.Ident id ?? "expected identifier after for";
+ 'Token.Kwd '=' ?? "expected '=' after for";
+ stream >] ->
+ begin parser
+ | [<
+ start=parse_expr;
+ 'Token.Kwd ',' ?? "expected ',' after for";
+ end_=parse_expr;
+ stream >] ->
+ let step =
+ begin parser
+ | [< 'Token.Kwd ','; step=parse_expr >] -> Some step
+ | [< >] -> None
+ end stream
+ in
+ begin parser
+ | [< 'Token.In; body=parse_expr >] ->
+ Ast.For (id, start, end_, step, body)
+ | [< >] ->
+ raise (Stream.Error "expected 'in' after for")
+ end stream
+ | [< >] ->
+ raise (Stream.Error "expected '=' after for")
+ end stream
+
+ | [< >] -> raise (Stream.Error "unknown token when expecting an expression.")
+
+(* unary
+ * ::= primary
+ * ::= '!' unary *)
+and parse_unary = parser
+ (* If this is a unary operator, read it. *)
+ | [< 'Token.Kwd op when op != '(' && op != ')'; operand=parse_expr >] ->
+ Ast.Unary (op, operand)
+
+ (* If the current token is not an operator, it must be a primary expr. *)
+ | [< stream >] -> parse_primary stream
+
+(* binoprhs
+ * ::= ('+' primary)* *)
+and parse_bin_rhs expr_prec lhs stream =
+ match Stream.peek stream with
+ (* If this is a binop, find its precedence. *)
+ | Some (Token.Kwd c) when Hashtbl.mem binop_precedence c ->
+ let token_prec = precedence c in
+
+ (* If this is a binop that binds at least as tightly as the current binop,
+ * consume it, otherwise we are done. *)
+ if token_prec < expr_prec then lhs else begin
+ (* Eat the binop. *)
+ Stream.junk stream;
+
+ (* Parse the unary expression after the binary operator. *)
+ let rhs = parse_unary stream in
+
+ (* Okay, we know this is a binop. *)
+ let rhs =
+ match Stream.peek stream with
+ | Some (Token.Kwd c2) ->
+ (* If BinOp binds less tightly with rhs than the operator after
+ * rhs, let the pending operator take rhs as its lhs. *)
+ let next_prec = precedence c2 in
+ if token_prec < next_prec
+ then parse_bin_rhs (token_prec + 1) rhs stream
+ else rhs
+ | _ -> rhs
+ in
+
+ (* Merge lhs/rhs. *)
+ let lhs = Ast.Binary (c, lhs, rhs) in
+ parse_bin_rhs expr_prec lhs stream
+ end
+ | _ -> lhs
+
+(* expression
+ * ::= primary binoprhs *)
+and parse_expr = parser
+ | [< lhs=parse_unary; stream >] -> parse_bin_rhs 0 lhs stream
+
+(* prototype
+ * ::= id '(' id* ')'
+ * ::= binary LETTER number? (id, id)
+ * ::= unary LETTER number? (id) *)
+let parse_prototype =
+ let rec parse_args accumulator = parser
+ | [< 'Token.Ident id; e=parse_args (id::accumulator) >] -> e
+ | [< >] -> accumulator
+ in
+ let parse_operator = parser
+ | [< 'Token.Unary >] -> "unary", 1
+ | [< 'Token.Binary >] -> "binary", 2
+ in
+ let parse_binary_precedence = parser
+ | [< 'Token.Number n >] -> int_of_float n
+ | [< >] -> 30
+ in
+ parser
+ | [< 'Token.Ident id;
+ 'Token.Kwd '(' ?? "expected '(' in prototype";
+ args=parse_args [];
+ 'Token.Kwd ')' ?? "expected ')' in prototype" >] ->
+ (* success. *)
+ Ast.Prototype (id, Array.of_list (List.rev args))
+ | [< (prefix, kind)=parse_operator;
+ 'Token.Kwd op ?? "expected an operator";
+ (* Read the precedence if present. *)
+ binary_precedence=parse_binary_precedence;
+ 'Token.Kwd '(' ?? "expected '(' in prototype";
+ args=parse_args [];
+ 'Token.Kwd ')' ?? "expected ')' in prototype" >] ->
+ let name = prefix ^ (String.make 1 op) in
+ let args = Array.of_list (List.rev args) in
+
+ (* Verify right number of arguments for operator. *)
+ if Array.length args != kind
+ then raise (Stream.Error "invalid number of operands for operator")
+ else
+ if kind == 1 then
+ Ast.Prototype (name, args)
+ else
+ Ast.BinOpPrototype (name, args, binary_precedence)
+ | [< >] ->
+ raise (Stream.Error "expected function name in prototype")
+
+(* definition ::= 'def' prototype expression *)
+let parse_definition = parser
+ | [< 'Token.Def; p=parse_prototype; e=parse_expr >] ->
+ Ast.Function (p, e)
+
+(* toplevelexpr ::= expression *)
+let parse_toplevel = parser
+ | [< e=parse_expr >] ->
+ (* Make an anonymous proto. *)
+ Ast.Function (Ast.Prototype ("", [||]), e)
+
+(* external ::= 'extern' prototype *)
+let parse_extern = parser
+ | [< 'Token.Extern; e=parse_prototype >] -> e
projects / oota-llvm.git / blobdiff