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
|
#include <u.h>
#include <libc.h>
#include "dat.h"
#include "fns.h"
int builtinfail(Term *, Term *, Goal **, Choicepoint **, Binding **);
int builtincall(Term *, Term *, Goal **, Choicepoint **, Binding **);
int builtincut(Term *, Term *, Goal **, Choicepoint **, Binding **);
Builtin
findbuiltin(Term *goal)
{
int arity;
Rune *name;
switch(goal->tag){
case AtomTerm:
arity = 0;
name = goal->text;
break;
case CompoundTerm:
arity = goal->arity;
name = goal->text;
break;
default:
return nil;
}
if(!runestrcmp(name, L"fail") && arity == 0)
return builtinfail;
if(!runestrcmp(name, L"call") && arity == 1)
return builtincall;
if(!runestrcmp(name, L"!") && arity == 0)
return builtincut;
return nil;
}
int
builtinfail(Term *database, Term *goal, Goal **goals, Choicepoint **choicestack, Binding **bindings)
{
USED(database);
USED(goal);
USED(goals);
USED(choicestack);
USED(bindings);
return 0;
}
int
builtincall(Term *database, Term *goal, Goal **goals, Choicepoint **choicestack, Binding **bindings)
{
USED(database);
USED(choicestack);
USED(bindings);
Goal *g = malloc(sizeof(Goal));
g->goal = goal->children;
g->next = *goals;
*goals = g;
return 1;
}
int
builtincut(Term *database, Term *goal, Goal **goals, Choicepoint **choicestack, Binding **bindings)
{
USED(database);
USED(goals);
USED(bindings);
Choicepoint *cp = *choicestack;
/* Cut all choicepoints with an id larger or equal to the goal clause number, since they must have been introduced
after this goal's parent.
*/
while(cp != nil && cp->id >= goal->clausenr)
cp = cp->next;
*choicestack = cp;
return 1;
}
|