Make length, etc. members?

[matthewleon]

In Haskell's Data.Foldable, a lot of the utility functions are class members, allowing for instances to define more efficient implementations. What do people think of potentially doing this here?

[garyb]

Until we have default member implementations we don't want to do this, as implementing 20+ functions rather than 2 or 3 is a little unreasonable for instance-writers to be expected to deal with.