Re: Ann: SWI-Prolog 7.1.0

On 7/12/2013, at 10:54 PM, Jan Wielemaker wrote:
> 
> All true.  Just, Prolog systems can also nicely generate a switch-on-tag
> from code such as
> 
> do(X) :- atom(X), ....
> do(X) :- number(X), ...
> do(X) :- string(X), ...

Some can, some can't, some could but don't.
For what it's worth, in Xerox Quintus Prolog, numbers (other
than immediate integers) and strings had the *same* tag.

> 
> etc.  Properly implemented, the above should be faster than code like this
> 
> do(atom(X)) :-
> do(number(X)) :-
> do(string(X)) :-

That's *if* the distinctions you want to make are aligned
with Prolog built-in types.