Hilog supports something called "generic programs". You can think of
these as query literals you can pass around and call, bit like function
literals.
Because Hilog is untyped it uses a separate parenthesis to allow query
literals to be passed:
http://www.cs.sunysb.edu/~warren/xsbbook/node46.html
"... snip ....
closure(R)(X,Y) :- R(X,Y).
closure(R)(X,Y) :- R(X,Z), closure(R)(Z,Y).
Now given any binary relation, one can use use this definition to
compute its closure. For example, we can define a binary predicate,
|parent| as follows:
:- hilog parent.
parent(able,adam).
parent(able,eve).
parent(cain,adam).
parent(cain,eve).
etc
and then we can use the generic definition of closure to find anscestors:
| ?- clo
... snip ...."
We could supprt this if we added generics to our query literals, probably
something like:
query closure( Query<String, String> q, String x, String y )
q( x, y )
or
( q( x, z ) and q(z, y) )
end
Anyway something worth thinking on, when we start to look at function literal
support in Drools, we should probably address the two at the same time.
Mark
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