Class LAcond

Object
   |
   +--Lens
         |
         +--LAcond

class LAcond

extends Lens

Applies one of two lenses based on predicates on the concrete and abstract trees. LAcond behaves like LCcond, only a separate predicate pa determines which lens to use during putback, making this lens (slightly) more oblivious.

The lens is not oblivious because different lenses may be used for get and putback; if this is the case, then the undefined is given instead of c.

LAcond is typically used to dispatch subtypes to appropriate lenses. For an example, see LRenameIfPresent, which is essentially:

For simply dispatching, LCcond may be sufficient.

- LCcond
- LCond

Field Detail

name

Object name

LAcond

LAcond(<Predicate> pc, <Predicate> pa, <Predicate> pass_lens, <Predicate> fail_lens)

Parameters:
pc - A predicate on the concrete tree
pa - A predicate on the abstract tree
pass_lens - Used for get when pc matches the concrete tree; used for putback when pa matches a
fail_lens - Used for get when pc does not match the concrete tree; used for putback when a does not match pa

See:
- LCcond
- LCond

get

Object get(c)

putback

Object putback(a, c)