On Jan 12, 2010, at 5:04 AM, Sturla Molden wrote:
> I'd like to make a different suggestion. What about a keyword to pass
> after cdef in the declaration of the object to indicate the vtab can
> be skipped? I e an assertion that the object will be of the declared
> type. This will maintain better compatibility with Python.
>
> cdef Foo bar = Foo()
> cdef inline Foo fastbar = bar
Hmm... The notion of an "inline object" to me evokes allocating on the
stack, or passing by value, or something like that--not ignoring type
information when doing method dispatching. This isn't too important--
another keyword could be found.
> bar.method() # through vtab
> fastbar.method() # direct call
There is already a more explicit way to get this behavior:
cdef class A:
cdef identify(self):
print "I'm an A"
cdef class B(A):
cdef identify(self):
print "I'm a B"
cdef A a = A()
cdef B b = B()
a.identify() # prints "I'm an A"
b.identify() # prints "I'm a B"
A.identify(b) # prints "I'm an A"
It could probably be optimized to a direct call if desired by making
the type vtab store const function pointers.
In any case, a non-overridable inline cdef method doesn't break Python
semantics. (Well, you can't override it, but that's caught at compile
time, rather than potentially surprising an end user at runtime.)
- Robert
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