1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
| (*===---------------------------------------------------------------------===
* 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 *)
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
| [< >] -> raise (Stream.Error "unknown token when expecting an expression.")
(* 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 primary expression after the binary operator. *)
let rhs = parse_primary 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_primary; stream >] -> parse_bin_rhs 0 lhs stream
(* prototype
* ::= id '(' id* ')' *)
let parse_prototype =
let rec parse_args accumulator = parser
| [< 'Token.Ident id; e=parse_args (id::accumulator) >] -> e
| [< >] -> accumulator
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))
| [< >] ->
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
|