* Refactoring: put the Nix expression evaluator in its own library so

that it can be used by multiple programs.

src/libexpr/primops.hh

@@ -0,0 +1,34 @@
+#ifndef __PRIMOPS_H
+#define __PRIMOPS_H
+
+#include "eval.hh"
+
+
+/* Load and evaluate an expression from path specified by the
+   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
+   attributes: `outPath' containing the primary output path of the
+   derivation; `drvPath' containing the path of the Nix expression;
+   and `type' set to `derivation' to indicate that this is a
+   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);
+
+/* Determine whether the argument is the null value. */
+Expr primIsNull(EvalState & state, Expr arg);
+
+
+#endif /* !__PRIMOPS_H */