Michael Fischer:
# On Nov 04, Brent Dax <[EMAIL PROTECTED]> took up a keyboard
# and banged out
# > Michael Fischer:
# > # In the goto case, we spin. And perhaps I am broken there. End
# > # really wants to return, not just set the pc, but I hadn't thought
# > # of a clever way to do that corner case, and wanted to see what
# > # the behavior would be without it. I suspect I need it.
# >
# > Can't you just break()?
#
# Out of a function?
Isn't the win in computed goto that you inline the sub bodies and can
loop implicitly instead of explicitly, thus saving a jump or two?
goto *lookup[*pc];
op0:
return;
op1:
pc += 1;
goto *lookup[*pc];
op2:
/* whatever */
pc += size_of_op_2;
goto lookup[*pc];
op3:
/* this one may halt */
if(whatever) {
pc += size_of_op_3;
goto lookup[*pc];
}
else {
return;
}
vs.
while(pc) {
goto *lookup[*pc];
op0:
pc=Parrot_op_end(pc, interp);
continue;
op1:
pc=Parrot_op_noop(pc, interp);
continue;
op2:
pc=Parrot_op_whatever(pc, interp);
continue;
op3:
pc=Parrot_op_whatever_else(pc, interp);
continue;
...
}
The second example really is no better than a switch (and perhaps worse,
since the compiler can't get a high-level view of things and maybe come
up with a better way to do it).
--Brent Dax
[EMAIL PROTECTED]
Configure pumpking for Perl 6
When I take action, I'm not going to fire a $2 million missile at a $10
empty tent and hit a camel in the butt.
--Dubya
