I think they should be mentioned in the interface docs, so that if they are implemented by an ADT it's done in a uniform way. Like many other functions, they might very well be optional.
Anyway, it's not a problem to add them later on; they are de facto fairly well defined (i.e. an ADT implementing e.g. `| ought to do it in the same way as it works on arrays, multisets and mappings already), so it's mostly a matter of writing it down.
/ Martin Stjernholm, Roxen IS
Previous text:
2002-11-09 20:13: Subject: More about ADTs
Yes I know, actually it was a deliberate choise to leave them outside the interface. Since i try to keep the interface as small as possible, just basic, and the +. -, /, %, &, | only work on some ADTs and not others i decided to put them on ADT level instead of on this interface level.
/ Peta, jo det är jag