[Libre-soc-bugs] [Bug 1094] insndb instruction database visitor-walker is needed

[bugzilla-daemon at libre-soc.org]

https://bugs.libre-soc.org/show_bug.cgi?id=1094

--- Comment #158 from Jacob Lifshay <programmerjake at gmail.com> ---
(In reply to Dmitry Selyutin from comment #156)
> (In reply to Dmitry Selyutin from comment #155)
> > I think we can leave the short form, but internally we can implement
> > everything as callables. Holy cow that's really powerful!
> 
> 
> Nah, implementing everything as callables loses one benefit: we can have
> hash lookup with types, with callables we're limited to linear search. It's
> not that it's critical (who's crazy to establish thousands of hooks?), but
> it hurts the beauty of the code. I'm currently checking something more
> graceful.

if you're worried about speed, you could cache lookups -- something like:

class Visitor:
    def __init__(self):
        self.__cache = {}
    def run_hook(self, v):
        t = v if isinstance(v, type) else type(v)
        f = self.__cache.get(t)
        if f is None:
            for name, check in self.hooks():
                if check(t):
                    self.__cache[t] = f = getattr(self, name)
                    break
            if f is None:
                raise TypeError("no hooks for type", t)
        return f(v)

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