diff options
| -rw-r--r-- | prolog/engine.py | 89 |
1 files changed, 85 insertions, 4 deletions
diff --git a/prolog/engine.py b/prolog/engine.py index f8e563f..b0dc1aa 100644 --- a/prolog/engine.py +++ b/prolog/engine.py @@ -4,7 +4,10 @@ import collections import html import http.client import json +from operator import itemgetter import re +import socket +import time import urllib def strip_html(text): @@ -123,9 +126,87 @@ def pretty_vars(data): result += [strip_html(b) for b in data['residuals']] return ',\n'.join(result) if result else 'true' +# Get all solutions to [query] given background knowledge [code] that are found +# within [timeout] seconds. +def run(code, query, timeout): + # Returns a tuple ((bindings, constraints), error, more?) for one answer. + def process_answer(reply): + # When an engine is destroyed, a nested data object has the actual + # query result. + if reply['event'] == 'destroy': + reply = reply['data'] + + if reply['event'] == 'success': + # Return a dictionary {var: value} and a list of constraints (as + # strings) from the JSON object returned by Prolog. + data = reply['data'][0] + bindings = {} + for binding in data['variables']: + value = strip_html(binding['value']) + for name in binding['variables']: + bindings[name] = value + constraints = [strip_html(r) for r in data.get('residuals', [])] + return (bindings, constraints), None, reply['more'] + elif reply['event'] == 'failure': + return None, None, False + elif reply['event'] == 'error': + # Remove potential module name (engine ID) from the error message. + error = ('error', reply['data'].replace("'{}':".format(reply['id']), '')) + return None, error, False + + start = time.monotonic() + result, messages = [], [] + engine = None + try: + # Create a new pengine. + reply, output = create(code=code, timeout=timeout) + messages += output + if reply.get('event') != 'create': + raise Exception('System error: creating pengine') + engine = reply['id'] + if 'error' in map(itemgetter(0), messages): + return None, messages + + # Run the query. + real_timeout = timeout - (time.monotonic()-start) + if real_timeout <= 0: + raise socket.timeout() + reply, output = ask(engine, query, real_timeout) + messages += output + if 'error' in map(itemgetter(0), output): + return None, messages + + bindings, error, more = process_answer(reply) + if bindings: + result.append(bindings) + if error: + messages.append(error) + + # Continue while there are more potential answers. + while more: + real_timeout = timeout - (time.monotonic()-start) + if real_timeout <= 0: + raise socket.timeout() + reply, output = next(engine, timeout=real_timeout) + messages += output + bindings, error, more = process_answer(reply) + if bindings: + result.append(bindings) + if error: + messages.append(error) + except socket.timeout as ex: + result.append('timeout') + abort(engine) + finally: + if engine: + destroy(engine) + + return result, messages + + # Basic sanity check. if __name__ == '__main__': - engine = create(code='dup([],[]). dup([H|T],[H,H|TT]) :- dup(T,TT).')['id'] - print('engine id is ' + engine) - print(ask(engine, "run_tests({}, Result)".format('dup/2'))) - destroy(engine) + answers, messages = run('b(Y). a(X) :- {X > 3}, (X = 5 ; {X > 4}).', 'a(X)', timeout=1) + print(messages) + for bindings, constraints in answers: + print('bindings: {}, constraints: {}'.format(bindings, constraints)) |