def unify(x, y, s={}):
"""Unify expressions x,y with substitution s; return a substitution that
would make x,y equal, or None if x,y can not unify. x and y can be
variables (e.g. Expr('x')), constants, lists, or Exprs. [Figure 9.1]
>>> unify(x, 3, {})
{x: 3}
"""
if s is None:
return None
elif x == y:
return s
elif is_variable(x):
return unify_var(x, y, s)
elif is_variable(y):
return unify_var(y, x, s)
elif isinstance(x, Expr) and isinstance(y, Expr):
return unify(x.args, y.args, unify(x.op, y.op, s))
elif isinstance(x, str) or isinstance(y, str):
return None
elif issequence(x) and issequence(y) and len(x) == len(y):
if not x:
return s
return unify(x[1:], y[1:], unify(x[0], y[0], s))
else:
return None
def unify(x, y, s={}):
"""Unify expressions x,y with substitution s; return a substitution that
would make x,y equal, or None if x,y can not unify. x and y can be
variables (e.g. Expr('x')), constants, lists, or Exprs. [Fig. 9.1]
>>> unify(P(x,y), P(a,b), {})
{y: b, x: a}
"""
if trace:
print "exp1:", x, " exp2:", y, " mu = ", s, "\n"
if s == None:
return None
elif x == y:
return s
# if any of therm is variable unify it with it's correspondent
elif is_variable(x):
return unify_var(x, y, s)
elif is_variable(y):
return unify_var(y, x, s)
# if they are expression
elif isinstance(x, Expr) and isinstance(y, Expr):
return unify(x.args, y.args, unify(x.op, y.op, s))
# if atom
elif isinstance(x, str) or isinstance(y, str) or not x or not y:
return s if x == y else None
# continue unification
elif issequence(x) and issequence(y) and len(x) == len(y):
return unify(x[1:], y[1:], unify(x[0], y[0], s))
else:
return None
def subset(self, indices):
'''Return a subset of the NumPy array.
@param indices: Row indices (ints).
@note: A I{subset} is different from a I{slice} in 2 ways:
(a) the I{subset} is typically specified as a list of
(un-)ordered indices and (b) the I{subset} allocates
a new, separate NumPy array while a I{slice} is just
an other I{view} of the original NumPy array.
@return: Sub-array (numpy.array).
@raise IndexError: Out of range indices value.
@raise TypeError: If indices is not a I{range} or a
I{list} of ints.
'''
if not issequence(indices, tuple): # NO tuple, only list
# and range work properly to get Numpy array sub-sets
raise TypeError('%s invalid: %s' % ('indices', type(indices)))
n = len(self)
for i, v in enumerate(indices):
if not isint(v):
raise TypeError('%s[%s] invalid: %r' % ('indices', i, v))
elif not 0 <= v < n:
raise IndexError('%s[%s] invalid: %r' % ('indices', i, v))
return self._subset(indices)
def unify(x, y, s):
if s is None:
return None
elif x == y:
return s
elif is_variable(x):
return unify_var(x, y, s)
elif is_variable(y):
return unify_var(y, x, s)
elif isinstance(x, Expr) and isinstance(y, Expr):
return unify(x.args, y.args, unify(x.op, y.op, s))
elif isinstance(x, str) or isinstance(y, str):
return None
elif issequence(x) and issequence(y) and len(x) == len(y):
if not x:
return s
return unify(x[1:], y[1:], unify(x[0], y[0], s))
else:
return None
def unify(x, y, s):
"""Unify expressions x,y with substitution s; return a substitution that
would make x,y equal, or None if x,y can not unify. x and y can be
variables (e.g. Expr('x')), constants, lists, or Exprs. [Figure 9.1]"""
if s is None:
return None
elif x == y:
return s
elif is_variable(x):
return unify_var(x, y, s)
elif is_variable(y):
return unify_var(y, x, s)
elif isinstance(x, Expr) and isinstance(y, Expr):
return unify(x.args, y.args, unify(x.op, y.op, s))
elif isinstance(x, str) or isinstance(y, str):
return None
elif issequence(x) and issequence(y) and len(x) == len(y):
if not x:
return s
return unify(x[1:], y[1:], unify(x[0], y[0], s))
else:
return None
def occur_check(var, x):
"""
Return true if var occurs anywhere in x.
"""
# if both are equal
if var == x:
return True
# if they are not and one the operands are equal or it's in occures in its variables
elif isinstance(x, Expr):
return var.op == x.op or occur_check(var, x.args)
# if it's list of arguments check every one
elif not isinstance(x, str) and issequence(x):
for xi in x:
if occur_check(var, xi):
return True
return False
