102 lines
2.9 KiB
Python
102 lines
2.9 KiB
Python
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import yap
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import sys
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# debugging support.
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import pdb
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def query_prolog(engine, s):
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def answer(q):
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try:
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return q.next()
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except Exception as e:
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print(e.args[1])
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return False
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#
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#construct a query from a one-line string
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# q is opaque to Python
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q = engine.query(s)
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# vs is the list of variables
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# you can print it out, the left-side is the variable name,
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# the right side wraps a handle to a variable
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vs = q.namedVars()
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# atom match either symbols, or if no symbol exists, sttrings, In this case
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# variable names should match strings
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for eq in vs:
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if not isinstance(eq[0],str):
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print( "Error: Variable Name matches a Python Symbol")
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return
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ask = True
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# launch the query
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while answer(q):
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# this new vs should contain bindings to vars
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vs= q.namedVars()
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#numbervars
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i=0
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# iteratw
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for eq in vs:
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name = eq[0]
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# this is tricky, we're going to bind the variables in the term so thay we can
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# output X=Y. The Python way is to use dictionares.
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#Instead, we use the T function to tranform the Python term back to Prolog
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binding = yap.T(eq[1])
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if binding.isVar():
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binding.unify(name)
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else:
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i = binding.numberVars(i, True)
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print(name + " = " + binding.text())
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#ok, that was Prolog code
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print("yes")
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# deterministic = one solution
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if q.deterministic():
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# done
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q.close()
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return
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if ask:
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s = input("more(;), all(*), no(\\n), python(#) ?").lstrip()
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if s.startswith(';') or s.startswith('y'):
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continue
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elif s.startswith('#'):
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try:
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exec(s.lstrip('#'))
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except:
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raise
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elif s.startswith('*') or s.startswith('a'):
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ask = False
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continue
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else:
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break
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print("No (more) answers")
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q.close()
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return
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def live():
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engine = yap.YAPEngine()
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loop = True
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pdb.set_trace()
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while loop:
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try:
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s = input("?- ")
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if not s:
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loop = False
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query_prolog(engine, s)
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except SyntaxError as err:
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print("Syntax Error error: {0}".format(err))
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except EOFError:
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return
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except RuntimeError as err:
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print("YAP Execution Error: {0}".format(err))
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except ValueError:
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print("Could not convert data to an integer.")
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except:
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print("Unexpected error:", sys.exc_info()[0])
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raise
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engine.close()
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#
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# initialize engine
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# engine = yap.YAPEngine();
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# engine = yap.YAPEngine(yap.YAPParams());
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#live()
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