From 42f7fd57532c62e1de352061f4eb3386ab42ed3e Mon Sep 17 00:00:00 2001
From: Aleksander Sadikov <sasha@fri.uni-lj.si>
Date: Thu, 10 Sep 2015 20:03:26 +0200
Subject: Update prolog engine (sasha's aux functions for prolog hint testing
 added).

---
 prolog/engine.py | 98 +++++++++++++++++++++++++++++++++++++++++---------------
 1 file changed, 73 insertions(+), 25 deletions(-)

(limited to 'prolog/engine.py')

diff --git a/prolog/engine.py b/prolog/engine.py
index 91c6172..50582c8 100644
--- a/prolog/engine.py
+++ b/prolog/engine.py
@@ -115,32 +115,8 @@ def pretty_vars(data):
 # Run [query] in the pengine with id [engine] and return the list of answers
 # found within [timeout] seconds. If a timeout occurs before the query is done,
 # 'timed out' is appended as the last answer.
-def ask_all(engine, query, timeout):
+def ask_all(engine, query, timeout=10):
     # 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()
     answers, messages = [], []
     try:
@@ -171,6 +147,78 @@ def ask_all(engine, query, timeout):
         answers.append('timed out')
     return answers, messages
 
+# Run [query] in the pengine with id [engine] and return the first answer only
+# found within [timeout] seconds.
+# used for quick hint debugging by Sasha
+def ask_one(engine, query, timeout=1):
+    # quicker than ask_all as there could be many hint-triggering tests
+    # Returns either an error message, true, false, timeout (see below), or bindings
+    # Timeout is "returned" as an unhandled exception -- deliberately so
+
+    # Run the query.
+    reply, output = ask(engine, query, timeout)
+    if 'error' in map(itemgetter(0), output):
+        return 'query syntax error'
+        # TODO: Tim, this doesn't really work. It just proceeds and returns as a runtime error.
+    answer, error, more = process_answer(reply)
+    if error:
+        # query caused a runtime error
+        return 'runtime error: ' + error[-1]
+    elif answer:
+        # no error, query satisfied
+        if not answer[0]:       # empty bindings
+            return 'true'
+        else:
+            return answer[0]    # for now return just bindings without constraints
+    else:
+        # no error, query failed
+        return 'false'
+
+def ask_truth(engine, query, timeout=1):
+    # quicker than ask_all as there could be many hint-triggering tests
+    # Returns either True or False
+    # (Runtime) error is False!
+    # Timeout is an unhandled exception -- deliberately so
+
+    # Run the query.
+    reply, output = ask(engine, query, timeout)
+    if 'error' in map(itemgetter(0), output):
+        return False
+        # TODO: Tim, this doesn't really work. It just proceeds and returns as a runtime error.
+    answer, error, more = process_answer(reply)
+    if error:
+        # query caused a runtime error
+        return False
+    elif answer:
+        return True
+    else:
+        # no error, query failed
+        return False
+
+# reformats prolog's answer into a neater form
+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
 
 # Basic sanity check.
 if __name__ == '__main__':
-- 
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