J A small problem

While trying to solve this problem with J, I got a trouble. It will look elegantly if to write the implicit definition of the following operator H:

x H y 
  (x F y) G x

I do not get it...

The trivial explisit solution, which is not so elegant ;)

H =: 3 : 0
    (F~ y.) G y.
:
    (x. F y.) G x.
)

(09-12-2005), Update: Oops, I got it wrong...

H=:(f g [)