Added a short comment explaining the choice of AnyDataItem in TreeUtil

2007-09-11 22:58:58 +00:00 · 2007-09-11 22:58:58 +00:00 · dbdef53e31
commit dbdef53e31
parent 8514823f1f
1 changed files with 2 additions and 0 deletions
--- a/common/TreeUtil.hs
+++ b/common/TreeUtil.hs
@ -31,6 +31,8 @@ type MatchErrors = [String]

 -- | A data item used when matching items of interest.  Note that it is similar to Pattern but not the same;
 --   AnyDataItem can only contain Data, and has no other special values.
+--   We do not use Data.Dynamic because Dynamic only requires Typeable a; we want Data a to enable us
+--   to test the items for equality.
 data AnyDataItem = forall a. Data a => ADI a

 instance Show AnyDataItem where