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

that it can be used by multiple programs.

src/libexpr/eval.hh

@@ -0,0 +1,42 @@
+#ifndef __EVAL_H
+#define __EVAL_H
+
+#include <map>
+
+#include "aterm.hh"
+#include "hash.hh"
+#include "nixexpr.hh"
+
+
+typedef map<Path, PathSet> DrvPaths;
+typedef map<Path, Hash> DrvHashes;
+
+struct EvalState 
+{
+    ATermMap normalForms;
+    DrvPaths drvPaths;
+    DrvHashes drvHashes; /* normalised derivation hashes */
+    Expr blackHole;
+
+    unsigned int nrEvaluated;
+    unsigned int nrCached;
+
+    EvalState();
+};
+
+
+/* Evaluate an expression to normal form. */
+Expr evalExpr(EvalState & state, Expr e);
+
+/* Evaluate an expression read from the given file to normal form. */
+Expr evalFile(EvalState & state, const Path & path);
+
+/* Specific results. */
+string evalString(EvalState & state, Expr e);
+Path evalPath(EvalState & state, Expr e);
+
+/* Print statistics. */
+void printEvalStats(EvalState & state);
+
+
+#endif /* !__EVAL_H */