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
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
|
#!/usr/bin/python3
from prolog.core import *
from prolog.util import *
class Atom(object):
__slots__ = 'ref'
def __init__(self, val=None, ref=None):
if ref is not None:
self.ref = ref
return
self.ref = PL_new_atom(bytes(val, encoding=encoding))
class Term(object):
__slots__ = 'ref'
# Initialize from term reference [ref] if given, otherwise construct a new
# term from [val] and possibly [args].
def __init__(self, val=None, args=None, ref=None):
if ref is not None:
self.ref = ref
return
self.ref = PL_new_term_ref()
if isinstance(val, str):
if args is not None:
# Explicitly constructed compound term with name [val] and arguments [args].
name = PL_new_atom(bytes(val, encoding=encoding))
PL_cons_functor_v(self.ref, PL_new_functor(name, len(args)), Termv(args).ref)
else:
# Parse term from [val].
if not PL_chars_to_term(bytes(val, encoding=encoding), self.ref):
raise ValueError('invalid compound term')
elif isinstance(val, int):
PL_put_integer(self.ref, val)
elif isinstance(val, float):
PL_put_float(self.ref, val)
elif isinstance(val, list):
PL_put_nil(self.ref)
for t in val:
PL_cons_list(self.ref, t.ref, self.ref)
elif isinstance(val, Atom):
PL_put_atom(self.ref, val.ref)
def __iter__(self):
if not PL_is_list(self.ref):
raise TypeError('term is not a list')
ref = self.ref
head, tail = Term(), Term()
while PL_get_list(ref, head.ref, tail.ref):
yield head
ref = tail.ref
def __str__(self):
ptr = c_char_p()
if PL_get_chars(self.ref, byref(ptr), CVT_WRITE|BUF_RING):
return str(ptr.value, encoding=encoding)
class Termv(object):
__slots__ = 'ref'
def __init__(self, terms):
self.ref = PL_new_term_refs(len(terms))
for i, term in enumerate(terms):
PL_put_term(self.ref+i, term.ref)
class PrologEngine(object):
def __init__(self):
# initialize Prolog library
args = ['./', '-q', '--nosignals']
if SWI_HOME_DIR is not None:
args.append('--home={0}'.format(SWI_HOME_DIR))
s_plargs = len(args)
plargs = (c_char_p*s_plargs)()
for i in range(s_plargs):
plargs[i] = bytes(args[i], encoding)
if not PL_initialise(s_plargs, plargs):
raise EnvironmentError('Could not initialize Prolog environment.'
'PL_initialise returned {0}'.format(result))
# construct some predicates
self.p = {
'assertz': PL_predicate(b'assertz', 2, None),
'erase': PL_predicate(b'erase', 1, None),
'call_with_depth_limit': PL_predicate(b'call_with_depth_limit', 3, None),
'call_with_time_limit': PL_predicate(b'call_with_time_limit', 2, None),
'consult': PL_predicate(b'consult', 1, None),
'findnsols': PL_predicate(b'findnsols', 4, None),
'message_to_string': PL_predicate(b'message_to_string', 2, None),
'read_term_from_atom': PL_predicate(b'read_term_from_atom', 3, None),
'safe_goal': PL_predicate(b'safe_goal', 1, None),
'set_prolog_stack': PL_predicate(b'set_prolog_stack', 2, None)
}
self.err_flags = PL_Q_NODEBUG|PL_Q_CATCH_EXCEPTION
# database of current asserts; each load gets a new index
self.refs = {}
self.max_index = 0
# increase memory limits
self.call('set_prolog_stack', [Term('global'), Term('limit(2*10**9)')])
self.call('set_prolog_stack', [Term('local'), Term('limit(2*10**9)')])
# discard messages from swipl library
self.load('message_hook(_, _, _). ')
def exception(self, qid):
ref = PL_exception(qid)
if ref is None:
return False
try:
ex = Term(ref=ref)
if ex is not None:
msg = Term()
if PL_call_predicate(None, self.err_flags,
self.p['message_to_string'], Termv([ex, msg]).ref):
raise Exception(str(msg))
raise Exception('Unknown error')
finally:
PL_clear_exception()
return False
def call(self, name, args):
qid = PL_open_query(None, self.err_flags, self.p[name], Termv(args).ref)
try:
if not PL_next_solution(qid):
if not self.exception(qid):
return False
finally:
PL_cut_query(qid)
return True
def consult(self, filename):
return self.call('consult', [Term(Atom(filename))])
def load(self, program, module=None):
tokens = tokenize(program)
refs = []
try:
start = 0
for idx in range(len(tokens)):
if tokens[idx].type != 'PERIOD' or idx - start <= 1:
continue
rule = stringify(tokens[start:idx])
orig_rule = rule
start = idx + 1
if module is not None:
rule = module + ':(' + rule + ')'
ref = Term()
if self.call('assertz', [Term(rule), ref]):
refs.append(ref)
except Exception as ex:
# unload already loaded rules (hacky, mustfix, todo)
for ref in refs:
self.call('erase', [ref])
raise Exception('Error loading program: {}\nBad rule: {}'.format(ex, orig_rule))
self.max_index += 1
self.refs[self.max_index] = refs
return self.max_index
def unload(self, index):
try:
for ref in self.refs[index]:
self.call('erase', [ref])
del self.refs[index]
except Exception as ex:
# This should never happen.
sys.stderr.write(str(ex) + '\n')
# Get up to [n] solutions to query [q].
def query(self, q, module=None, n=1):
if module is not None:
q = '{}:({})'.format(module, q)
fid = PL_open_foreign_frame()
var_names = Term()
options = Term([Term('variable_names', [var_names])])
goal = Term()
try:
# Parse term and store variable names.
if not self.call('read_term_from_atom', [Term(Atom(q)), goal, options]):
raise Exception('Warning: Could not read term from {}\n'.format(q))
# Check if goal is safe with currently loaded rules.
if not self.call('safe_goal', [goal]):
raise Exception('Warning: Unsafe goal: {}\n'.format(goal))
except Exception as ex:
raise
solutions = Term()
goal_aux = Term('findnsols', [Term(n), goal, goal, solutions])
qid = PL_open_query(None, self.err_flags, self.p['call_with_time_limit'],
Termv([Term(0.01), goal_aux]).ref)
result = []
if PL_next_solution(qid):
for solution in solutions:
fid_solution = PL_open_foreign_frame()
PL_unify(goal.ref, solution.ref)
variables = {}
for var in var_names:
name, value = Term(), Term()
PL_get_arg(1, var.ref, name.ref)
PL_get_arg(2, var.ref, value.ref)
variables[str(name)] = str(value)
result.append(variables)
PL_rewind_foreign_frame(fid_solution)
else:
self.exception(qid)
PL_close_query(qid)
PL_discard_foreign_frame(fid)
return result
# Basic sanity check.
if __name__ == '__main__':
prolog = PrologEngine()
prolog.load('a(1). a(2). a(3).', 'test')
n = 1
while True:
solution = prolog.query('a(X), a(Y), X\=Y', 'test', n=n)
if solution is None or len(solution) != n:
print('{} solutions found!'.format(n-1))
break
print(solution[-1])
n += 1
|
