- Datatype package now also supports arbitrarily branching datatypes
(using function types).
- Added new simplification procedure for proving distinctness of
constructors.
- dtK is now a reference.
consts last :: 'a list => 'a
recdef last "measure (%xs. length xs)"
"last [x] = x"
"last (x#y#zs) = last (y#zs)"