Annotation of /sml/trunk/src/ml-yacc/examples/calc/calc.grm

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1 :	monnier	2	(* Sample interactive calculator for ML-Yacc *)
2 :
3 :			fun lookup "bogus" = 10000
4 :			| lookup s = 0
5 :
6 :			%%
7 :
8 :			%eop EOF SEMI
9 :
10 :			(* %pos declares the type of positions for terminals.
11 :			Each symbol has an associated left and right position. *)
12 :
13 :			%pos int
14 :
15 :			%left SUB PLUS
16 :			%left TIMES DIV
17 :			%right CARAT
18 :
19 :			%term ID of string | NUM of int | PLUS | TIMES | PRINT |
20 :			SEMI | EOF | CARAT | DIV | SUB
21 :			%nonterm EXP of int | START of int option
22 :
23 :			%name Calc
24 :
25 :			%subst PRINT for ID
26 :			%prefer PLUS TIMES DIV SUB
27 :			%keyword PRINT SEMI
28 :
29 :			%noshift EOF
30 :			%value ID ("bogus")
31 :			%verbose
32 :			%%
33 :
34 :			(* the parser returns the value associated with the expression *)
35 :
36 :			START : PRINT EXP (print (Int.toString EXP);
37 :			print "\n";
38 :			SOME EXP)
39 :			| EXP (SOME EXP)
40 :			| (NONE)
41 :			EXP : NUM (NUM)
42 :			| ID (lookup ID)
43 :			| EXP PLUS EXP (EXP1+EXP2)
44 :			| EXP TIMES EXP (EXP1*EXP2)
45 :			| EXP DIV EXP (EXP1 div EXP2)
46 :			| EXP SUB EXP (EXP1-EXP2)
47 :			| EXP CARAT EXP (let fun e (m,0) = 1
48 :			| e (m,l) = m*e(m,l-1)
49 :			in e (EXP1,EXP2)
50 :			end)

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