AIMA.Core.Logic.FOL.Unifier.unify C# (CSharp) Метод

        public Dictionary<Variable, Term> unify(FOLNode x, FOLNode y,
                Dictionary<Variable, Term> theta)
        {
            // if theta = failure then return failure
            if (theta == null)
            {
                return null;
            }
            else if (x.Equals(y))
            {
                // else if x = y then return theta
                return theta;
            }
            else if (x is Variable)
            {
                // else if VARIABLE?(x) then return UNIVY-VAR(x, y, theta)
                return unifyVar((Variable)x, y, theta);
            }
            else if (y is Variable)
            {
                // else if VARIABLE?(y) then return UNIFY-VAR(y, x, theta)
                return unifyVar((Variable)y, x, theta);
            }
            else if (isCompound(x) && isCompound(y))
            {
                // else if COMPOUND?(x) and COMPOUND?(y) then
                // return UNIFY(x.ARGS, y.ARGS, UNIFY(x.OP, y.OP, theta))
                return unify(args(x), args(y), unifyOps(op(x), op(y), theta));
            }
            else
            {
                // else return failure
                return null;
            }
        }