1 files changed, 5 insertions, 0 deletions
diff --git a/src/libexpr/value.hh b/src/libexpr/value.hh
index 71025824e..1a0738241 100644
--- a/src/libexpr/value.hh
+++ b/src/libexpr/value.hh
@@ -166,6 +166,11 @@ struct Value
     {
         return type == tList1 ? 1 : type == tList2 ? 2 : bigList.size;
     }
+
+    /* Check whether forcing this value requires a trivial amount of
+       computation. In particular, function applications are
+       non-trivial. */
+    bool isTrivial() const;
 };