Use cons package

Author: brandonwillard

requirements.txt

@@ -9,6 +9,7 @@ pymc4 @ git+https://github.com/pymc-devs/pymc4.git@master#egg=pymc4-0.0.1
 multipledispatch>=0.6.0
 unification>=0.2.2
 kanren @ git+https://github.com/pymc-devs/kanren.git@symbolic-pymc#egg=kanren-0.2.3
+cons>=0.1.3
 toolz>=0.9.0
 sympy>=1.3
 cachetools

symbolic_pymc/relations/graph.py

@@ -5,7 +5,7 @@
 from kanren.core import goaleval
 
 from kanren import eq
-from kanren.cons import is_cons, is_null
+from cons.core import ConsPair, ConsNull
 from kanren.core import conde, lall
 from kanren.goals import conso, fail
 
@@ -75,11 +75,11 @@ def goal(s):
             l_out_, l_in_ = reify((l_out, l_in), s)
 
             out_null_type = False
-            if is_cons(l_out_) or is_null(l_out_):
+            if isinstance(l_out_, (ConsPair, ConsNull)):
                 out_null_type = type(l_out_)()
 
             in_null_type = False
-            if is_cons(l_in_) or is_null(l_in_):
+            if isinstance(l_in_, (ConsPair, ConsNull)):
                 in_null_type = type(l_in_)()
 
                 if out_null_type is not False and not type(in_null_type) == type(out_null_type):

symbolic_pymc/unify.py

@@ -2,6 +2,7 @@
 
 import numpy as np
 
+from cons import cdr
 from kanren.term import term, operator, arguments
 
 from unification.more import unify