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yap-6.3/packages/python/yapex.py
2018-03-26 11:03:08 +01:00

102 lines
2.9 KiB
Python

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