private static SubstitutionMap Unify(Atom a, Atom b, SubstitutionMap subMap)
{
var output = new SubstitutionMap(subMap);
if (a.Name != b.Name || a.Arguments.Count != b.Arguments.Count)
{
output.Failure = true;
return(output);
}
var atomA = new Atom(a);
var atomB = new Atom(b);
atomA.ApplySubMap(output);
atomB.ApplySubMap(output);
var disagreement = false;
for (var i = 0; i < atomA.Arguments.Count; i++)
{
var argA = atomA.Arguments[i];
var argB = atomB.Arguments[i];
if (argA.EqualTo(argB))
{
continue;
}
disagreement = true;
if (argA.CanMapTo(argB))
{
subMap.Add(argA, argB);
var newOutput = Unify(atomA, atomB, subMap);
newOutput.Changed = true;
return(newOutput);
}
if (argB.CanMapTo(argA))
{
subMap.Add(argB, argA);
var newOutput = Unify(atomA, atomB, subMap);
newOutput.Changed = true;
return(newOutput);
}
break;
}
if (disagreement)
{
output.Failure = true;
}
return(output);
}
private static SubstitutionMap UnifySubMap(SubstitutionMap subMapA, SubstitutionMap subMapB)
{
var output = new SubstitutionMap();
foreach (var keyA in subMapA.Keys)
{
if (subMapB.ContainsKey(keyA))
{
output.Failure = true;
return(output);
}
output.Add(keyA, subMapA.Get(keyA));
}
foreach (var keyB in subMapB.Keys)
{
output.Add(keyB, subMapB.Get(keyB));
}
return(output);
}