* Okay, that's a bit harder than expected.

1 files changed, 5 insertions, 2 deletions

diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index 58e6b40d7780..c95a309359af 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -48,8 +48,11 @@ Expr evalExpr(EvalState & state, Expr e);
 Expr evalFile(EvalState & state, const Path & path);
 
 /* Evaluate an expression, and recursively evaluate list elements and
-   attributes. */
-Expr strictEvalExpr(EvalState & state, Expr e);
+   attributes.  If `canonicalise' is true, we remove things like
+   position information and make sure that attribute sets are in
+   sorded order. */
+Expr strictEvalExpr(EvalState & state, Expr e,
+    bool canonicalise = false);
 
 /* Specific results. */
 string evalString(EvalState & state, Expr e);