1 files changed, 1 insertions, 0 deletions
diff --git a/common.sml b/common.sml
index 75ed15e..3fd58c2 100644
--- a/common.sml
+++ b/common.sml
@@ -2,6 +2,7 @@ exception Unreachable and Unimplemented
 
 fun $ (x, y) = x y
 infixr 0 $
+fun id x = x
 
 fun assert truth = if not truth then raise Unreachable else ()