From 4e7198a9c75e3c3839c73de295a9227dfb13d69b Mon Sep 17 00:00:00 2001
From: Timotej Lazar <timotej.lazar@araneo.org>
Date: Tue, 9 Dec 2014 15:49:26 +0100
Subject: Add a test to prolog.engine and clean up a bit

---
 prolog/engine.py | 40 ++++++++++++++++++++++++----------------
 1 file changed, 24 insertions(+), 16 deletions(-)

diff --git a/prolog/engine.py b/prolog/engine.py
index 92caa0a..2878933 100644
--- a/prolog/engine.py
+++ b/prolog/engine.py
@@ -66,7 +66,7 @@ class Termv(object):
 
 class PrologEngine(object):
     def __init__(self):
-        # initialize Prolog library
+        # Initialize the swipl library.
         args = ['./', '-q', '--nosignals']
         if SWI_HOME_DIR is not None:
             args.append('--home={0}'.format(SWI_HOME_DIR))
@@ -78,7 +78,7 @@ class PrologEngine(object):
             raise EnvironmentError('Could not initialize Prolog environment.'
                                    'PL_initialise returned {0}'.format(result))
 
-        # construct some predicates
+        # Construct some predicates.
         self.p = {
             'add_import_module/3': PL_predicate(b'add_import_module', 3, None),
             'assertz/1': PL_predicate(b'assertz', 1, None),
@@ -93,9 +93,6 @@ class PrologEngine(object):
         }
         self.err_flags = PL_Q_NODEBUG|PL_Q_CATCH_EXCEPTION
 
-        # Dictionary of correct answers; keys are (pid, query).
-        self.answers = {}
-
         # Increase memory limits.
         self.call('set_prolog_stack/2', [Term('global'), Term('limit(2*10**9)')])
         self.call('set_prolog_stack/2', [Term('local'), Term('limit(2*10**9)')])
@@ -103,18 +100,20 @@ class PrologEngine(object):
         # Discard messages from the swipl library.
         self.call('assertz/1', [Term('message_hook(_, _, _)')])
 
+        # Dictionary of correct answers; keys are (pid, query).
+        self.answers = {}
+
     def exception(self, qid):
         ref = PL_exception(qid)
-        if ref is None:
+        if not ref:
             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/2'], Termv([ex, msg]).ref):
-                    raise Exception(str(msg))
-                raise Exception('Unknown error')
+            msg = Term()
+            if PL_call_predicate(None, self.err_flags,
+                                 self.p['message_to_string/2'], Termv([ex, msg]).ref):
+                raise Exception(str(msg))
+            raise Exception('Unknown error')
         finally:
             PL_clear_exception()
         return False
@@ -220,9 +219,18 @@ class PrologEngine(object):
                 correct &= (len(result) == 1 and result[0]['X'] == self.answers[(pid, query)])
         except Exception as ex:
             correct = False
-        finally:
-            # Unload all loaded rules.
-            for ref in refs:
-                self.call('erase/1', [ref])
+
+        # Unload all loaded rules.
+        for ref in refs:
+            self.call('erase/1', [ref])
 
         return correct
+
+# Basic sanity check.
+if __name__ == '__main__':
+    engine = PrologEngine()
+    engine.consult('prolog/lib.pl')
+
+    engine.load_solution(0, 'a(2). a(2). a(3). ')
+    result = engine.test(0, 0, 'a(2). ', ['a(X)', 'a(Y), Y=X'])
+    print('{}: {}'.format(i, result))
-- 
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