Add a derive method

resolution.py

@@ -1,6 +1,6 @@
 from emis_funky_funktions import *
 
-from itertools import product
+from itertools import combinations, product
 
 from ir import Clause, IRNeg, IRProp, IRTerm, IRVar, Substitutions, sub_all, unify, unify_clauses
 
@@ -75,6 +75,26 @@ def merge_clauses(c1: Clause, c2: Clause) -> Sequence[Clause]:
         for (subs, i1, i2) in valid_substitutions
     ]
 
+def derive(clauses: Sequence[Clause]) -> Sequence[Clause]:
+    """
+    All possible clauses which derive in one step of resolution from a knowledge base
+
+    Attempts to merge every possible combination of clauses, in the knowledge base.
+
+    >>> derive([
+    ...     [IRNeg(IRProp('animal', [IRProp('Kim')]))],
+    ...     [IRNeg(IRProp('dog', [IRVar('x0')])), IRProp('animal', [IRVar('x0')])],
+    ...     [IRNeg(IRProp('cat', [IRVar('x1')])), IRProp('animal', [IRVar('x1')])],
+    ...     [IRProp('dog', [IRProp('Kim')])],
+    ... ])
+    [[¬dog(Kim())], [¬cat(Kim())], [animal(Kim())]]
+    """
+    return [
+        clause
+        for (c1, c2) in combinations(clauses, 2)
+        for clause in merge_clauses(c1, c2)
+    ]
+
 if __name__ == '__main__':
 	import doctest
 	doctest.testmod()