Re: [Boost-users] Why not overloading && and || in bind?

From: Peter Dimov (pdimov_at_[hidden])
Date: 2008-02-18 06:02:50

Richard:

> [Please do not mail me a copy of your followup]
>
> boost-users_at_[hidden] spake the secret code
> <011a01c87003$0ff77eb0$6407a80a_at_pdimov2> thusly:
>
>>[...] This thread did spark my interest though and I was able to add
>>&& and || to the trunk, complete with the proper short-circuit semantics.
>
> Can you elaborate on the approach you took?  I thought it was
> essentially impossible to replicate the short-circuit semantics with
> your own user-defined operator|| and operator&&.

It is impossible to overload && in such a way so that in e1 && e2, e2 is not 
evaluated when e1 is false. But it's possible to overload f && g so that in 
(f && g)(x) :- f(x) && g(x), g(x) is not evaluated when f(x) is false.