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
123
124
125
126
127
128
129
130
131
132
|
#include <stdio.h>
#include <stdlib.h>
// TODO: check erros and fail safely and
// see connection with the lexer
// Requirements
#include "parts/symbol.h"
#include "parts/grammar.h"
#include "parts/table.h"
#include "parts/toklist.h"
typedef int stack_item;
#define STACK_CAP 128
static stack_item stack_bottom[STACK_CAP];
static stack_item *stack_head = stack_bottom;
int lr_parser()
{
#define push(item) ({ if(++stack_head - stack_bottom < STACK_CAP ) (*stack_head = item); else { fprintf(stderr, "ERROR: STACK_CAP exceeded\n"); return 1; }})
#define pop() (--stack_head)
#define eat() toklist_eat()
#define peek() ({ \
symbol s = toklist_peek(); \
if(!symbol_is_valid(s)) { fprintf(stderr, "ERROR: Unknown token '%d'\n", s); return 1;} \
s; })
while(1) {
struct action a = table[(size_t)*stack_head][peek()];
switch(a.type) {
case ACTION_SHIFT:
push(eat());
push(a.arg);
break;
case ACTION_REDUCE:
for(size_t i = 0; i < 2*grammar[a.arg].nRHS; i++) pop();
symbol lhs = grammar[a.arg].LHS;
struct action a_goto = table[(size_t)*stack_head][lhs];
if(a_goto.type != ACTION_GOTO) {
fprintf(stderr,
"ERROR: Expected goto action for token '%d' at state %zu\n",
lhs, (size_t)*stack_head);
return 1;
}
push(lhs);
push(a_goto.arg);
break;
case ACTION_ACCEPT:
return 0;
case ACTION_NOT_SET:
default:
fprintf(stderr,
"ERROR: Unexpected token '%d' at state %zu\n",
peek(), (size_t)*stack_head);
return 1;
}
}
return 1;
}
#ifdef _LR_PARSER_STANDALONE
// implement symbol.h
enum symbol {
PLUS = 0,
MINUS,
LPAREN,
RPAREN,
N0, N1,
END_INPUT,
EP, E, T, N,
SYMBOLS_END,
};
size_t total_symbols = SYMBOLS_END;
IMPLEMENT_FUNCPTR(int, symbol_is_valid, (symbol s), { return s < SYMBOLS_END; })
// implement grammar.h
#define PROD(LHS, _, ...) {LHS, (symbol[]){__VA_ARGS__}, sizeof((symbol[]){__VA_ARGS__})/sizeof(symbol)}
static struct production _grammar[] = {
PROD(EP, ->, E, END_INPUT),
PROD(E, -->, E, PLUS, T),
PROD(E, -->, E, MINUS, T),
PROD(E, -->, T),
PROD(T, -->, LPAREN, E, RPAREN),
PROD(T, -->, N),
PROD(N, -->, N0),
PROD(N, -->, N1),
};
struct production *grammar = _grammar;
size_t total_productions = sizeof(_grammar)/sizeof(*_grammar);
// implement table.h
struct action **table = (struct action *([])){
(struct action[]){{0, 0},{0, 0},{1, 1},{0, 0},{1, 2},{1, 3},{0, 0},{0, 0},{2, 12},{2, 11},{2, 7},},
(struct action[]){{0, 0},{0, 0},{1, 1},{0, 0},{1, 2},{1, 3},{0, 0},{0, 0},{2, 4},{2, 11},{2, 7},},
(struct action[]){{3, 6},{3, 6},{0, 0},{3, 6},{0, 0},{0, 0},{3, 6},{0, 0},{0, 0},{0, 0},{0, 0},},
(struct action[]){{3, 7},{3, 7},{0, 0},{3, 7},{0, 0},{0, 0},{3, 7},{0, 0},{0, 0},{0, 0},{0, 0},},
(struct action[]){{1, 5},{1, 8},{0, 0},{1, 10},{0, 0},{0, 0},{0, 0},{0, 0},{0, 0},{0, 0},{0, 0},},
(struct action[]){{0, 0},{0, 0},{1, 1},{0, 0},{1, 2},{1, 3},{0, 0},{0, 0},{0, 0},{2, 6},{2, 7},},
(struct action[]){{3, 1},{3, 1},{0, 0},{3, 1},{0, 0},{0, 0},{3, 1},{0, 0},{0, 0},{0, 0},{0, 0},},
(struct action[]){{3, 5},{3, 5},{0, 0},{3, 5},{0, 0},{0, 0},{3, 5},{0, 0},{0, 0},{0, 0},{0, 0},},
(struct action[]){{0, 0},{0, 0},{1, 1},{0, 0},{1, 2},{1, 3},{0, 0},{0, 0},{0, 0},{2, 9},{2, 7},},
(struct action[]){{3, 2},{3, 2},{0, 0},{3, 2},{0, 0},{0, 0},{3, 2},{0, 0},{0, 0},{0, 0},{0, 0},},
(struct action[]){{3, 4},{3, 4},{0, 0},{3, 4},{0, 0},{0, 0},{3, 4},{0, 0},{0, 0},{0, 0},{0, 0},},
(struct action[]){{3, 3},{3, 3},{0, 0},{3, 3},{0, 0},{0, 0},{3, 3},{0, 0},{0, 0},{0, 0},{0, 0},},
(struct action[]){{1, 5},{1, 8},{0, 0},{0, 0},{0, 0},{0, 0},{4, 0},{0, 0},{0, 0},{0, 0},{0, 0},},
};
size_t table_states = 13;
// implement toklist
static symbol toklist[] = {N0, PLUS, N1, END_INPUT};
static symbol *tok = toklist;
symbol toklist_eat() { return *(tok++); } // unsafe
symbol toklist_peek() { return *tok; } // unsafe
int main(void)
{
return lr_parser();
}
#endif
|
