资料来源 : Free On-Line Dictionary of Computing

constant applicative form
     
        (CAF) (Functional programming) A {supercombinator} which is
        not a {lambda abstraction}.  This includes truly constant
        expressions such as 12, (+ 1 2), [1,2,3] as well as partially
        applied functions such as (+ 4).  Note that this last example
        is equivalent under {eta abstraction} to \ x . + 4 x which is
        not a CAF.
     
        Since a CAF is a supercombinator, it contains no free
        variables.  Moreover, since it is not a lambda abstraction it
        contains no variables at all.  It may however contain
        identifiers which refer to other CAFs, e.g.
     
        	c 3 where c = (* 2).
     
        A CAF can always be lifted to the top level of the program.
        It can either be compiled to a piece of graph which will be
        shared by all uses or to some shared code which will overwrite
        itself with some graph the first time it is evaluated.  A CAF
        such as
     
        	ints = from 1  where  from n = n : from (n+1)
     
        can grow without bound but may only be accessible from within
        the code of one or more functions.  In order for the {garbage
        collector} to be able to reclaim such structures, we associate
        with each function a list of the CAFs to which it refers.
        When garbage collecting a reference to the function we collect
        the CAFs on its list.
     
        (1994-11-30)