evaluator
Geoff Burn defines evaluators E0, E1, E2 and E3 which
when applied to an expression, reduce it to varying degrees.
E0 does no evaluation, E1 it evaluates to {weak head normal
form} (WHNF), E2 evaluates the structure of a list, i.e. it
evaluates it either to NIL or evaluates it to a CONS and then
applies E2 to the second argument of the CONS. E3 evaluates
the structure of a list and evaluates each element of the list
to {WHNF}. This concept can be extended to data structures
other than lists and forms the basis of the {evaluation
transformer} style of {strictness analysis}.
(1994-12-12)