* Assertions.

* Logical operators (!, &&, ||, ->).

src/fix-ng/primops.hh

@@ -8,7 +8,6 @@
    argument. */ 
 Expr primImport(EvalState & state, Expr arg);
 
-
 /* Construct (as a unobservable) side effect) a Nix derivation
    expression that performs the derivation described by the argument
    set.  Returns the original set extended with the following
@@ -18,14 +17,18 @@ Expr primImport(EvalState & state, Expr arg);
    derivation. */
 Expr primDerivation(EvalState & state, Expr args);
 
-
 /* Return the base name of the given string, i.e., everything
    following the last slash. */
 Expr primBaseNameOf(EvalState & state, Expr arg);
 
-
 /* Convert the argument (which can be a path or a uri) to a string. */
 Expr primToString(EvalState & state, Expr arg);
 
+/* Return the null value. */
+Expr primNull(EvalState & state, Expr arg);
+
+/* Determine whether the argument is the null value. */
+Expr primIsNull(EvalState & state, Expr arg);
+
 
 #endif /* !__PRIMOPS_H */