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
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
|
#include <stdlib.h>
#include <assert.h>
#include <stdio.h>
#include <term.h>
static int name_generator(void)
{
static int current = 0x424242; // TODO: idk?
return current++;
}
#define MAX_CONVERSION_VARS 256
static void to_barendregt_helper(struct term *term, int *vars, int size)
{
assert(size < MAX_CONVERSION_VARS);
switch (term->type) {
case ABS:
vars[size] = name_generator();
term->u.abs.name = vars[size];
to_barendregt_helper(term->u.abs.term, vars, size + 1);
break;
case APP:
to_barendregt_helper(term->u.app.lhs, vars, size);
to_barendregt_helper(term->u.app.rhs, vars, size);
break;
case VAR:
if (term->u.var.type == BARENDREGT_VARIABLE)
break;
int ind = size - term->u.var.name - 1;
if (ind < 0) {
fprintf(stderr, "Unbound variable %d\n",
term->u.var.name);
term->u.var.name = name_generator();
} else {
term->u.var.name = vars[size - term->u.var.name - 1];
}
term->u.var.type = BARENDREGT_VARIABLE;
break;
default:
fprintf(stderr, "Invalid type %d\n", term->type);
}
}
static void to_bruijn_helper(struct term *term, int *vars, int size)
{
assert(size < MAX_CONVERSION_VARS);
switch (term->type) {
case ABS:
vars[size] = term->u.abs.name;
to_bruijn_helper(term->u.abs.term, vars, size + 1);
term->u.abs.name = 0;
break;
case APP:
to_bruijn_helper(term->u.app.lhs, vars, size);
to_bruijn_helper(term->u.app.rhs, vars, size);
break;
case VAR:
if (term->u.var.type == BRUIJN_INDEX)
break;
int ind = -1;
for (int i = 0; i < size; i++) {
if (vars[i] == term->u.var.name) {
ind = i;
break;
}
}
if (ind < 0) {
fprintf(stderr, "Unbound variable %d\n",
term->u.var.name);
}
term->u.var.name = size - ind - 1;
term->u.var.type = BRUIJN_INDEX;
break;
default:
fprintf(stderr, "Invalid type %d\n", term->type);
}
}
void to_barendregt(struct term *term)
{
int vars[MAX_CONVERSION_VARS] = { 0 };
to_barendregt_helper(term, vars, 0);
}
void to_bruijn(struct term *term)
{
int vars[MAX_CONVERSION_VARS] = { 0 };
to_bruijn_helper(term, vars, 0);
}
struct term *new_term(term_type type)
{
struct term *term = calloc(1, sizeof(*term));
if (!term) {
fprintf(stderr, "Out of memory!\n");
abort();
}
term->type = type;
return term;
}
void free_term(struct term *term)
{
switch (term->type) {
case ABS:
free_term(term->u.abs.term);
free(term);
break;
case APP:
free_term(term->u.app.lhs);
free_term(term->u.app.rhs);
free(term);
break;
case VAR:
free(term);
break;
default:
fprintf(stderr, "Invalid type %d\n", term->type);
}
}
void print_term(struct term *term)
{
switch (term->type) {
case ABS:
if (term->u.abs.name)
printf("[{%d} ", term->u.abs.name);
else
printf("[");
print_term(term->u.abs.term);
printf("]");
break;
case APP:
printf("(");
print_term(term->u.app.lhs);
printf(" ");
print_term(term->u.app.rhs);
printf(")");
break;
case VAR:
printf("%d", term->u.var.name);
break;
default:
fprintf(stderr, "Invalid type %d\n", term->type);
}
}
void print_scheme(struct term *term)
{
switch (term->type) {
case ABS:
printf("(*lam \"%d\" ", term->u.abs.name);
print_scheme(term->u.abs.term);
printf(")");
break;
case APP:
printf("(*app ");
print_scheme(term->u.app.lhs);
printf(" ");
print_scheme(term->u.app.rhs);
printf(")");
break;
case VAR:
printf("(*var \"%d\")", term->u.var.name);
break;
default:
fprintf(stderr, "Invalid type %d\n", term->type);
}
}
|
