Minor doc

src/state.cpp

@@ -643,7 +643,7 @@ Expr State::mkExpr(Kind k, const std::vector<Expr>& children)
                 {
                   // if we failed to infer a nil terminator (likely due to
                   // a non-ground parameter), then we insert a placeholder
-                  // (alf.nil f t1 ... tn), which if t1...tn are non-ground
+                  // (alf.nil_of f t1 ... tn), which if t1...tn are non-ground
                   // will evaluate to the proper nil terminator when
                   // instantiated.
                   curr = mkExprInternal(Kind::EVAL_NIL_OF, vchildren);