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
|
%if False
> module Let7
> where
> import MLexer2
>
> data Expr = Const Int | Var String | Bin Expr Op Expr | Let Decl Expr
> deriving (Show)
>
> data Decl = String :=: Expr
> deriving (Show)
>
> expr :: (Monad m) => Lex m Expr
>
> %{
>
> Terminal = Numeral {Int}
> | Ident {String}
> | Addop {Op}
> | Mulop {Op}
> | KWLet as "let"
> | KWIn as "in"
> | Equal as "="
> | LParen as "("
> | RParen as ")"
> | *EOF;
>
> left 6 Addop {Op};
> left 7 Mulop {Op};
> nonassoc 0 "in";
%endif
> expr {Expr};
> expr {Const n} : Numeral {n};
> {Var s} | Ident {s};
> {Bin e1 op e2} | expr {e1}, Addop {op}, expr {e2};
> {Bin e1 op e2} | expr {e1}, Mulop {op}, expr {e2};
> {Let d e} | "let", decl {d}, "in", expr {e};
> {e} | "(", expr {e}, ")";
> {e} | "(", expr {e}, insert ")";
%if False
> decl {Decl};
> decl {s :=: e} : Ident {s}, "=", expr {e};
>
> }%
%endif
|
