On Jan 13, 2005, at 20:03, Clark C. Evans wrote:
Ok. I think we have identified two sorts of restrictions on the sorts of adaptations one may want to have:
`stateless' the adaptation may only provide a result which does not maintain its own state
`lossless' the adaptation preserves all information available in the original object, it may not discard state
If we determined that these were the 'big-ones', we could possibly allow for the signature of the adapt request to be parameterized with these two designations, with the default to accept any sort of adapter:
adapt(object, protocol, alternative = None, stateless = False, lossless = False)
__conform__(self, protocol, stateless, lossless)
__adapt__(self, object, stateless, lossless)
Then, Guido's 'Optional Static Typing',
def f(X: Y): pass
would be equivalent to
def f(X): X = adapt(Y, True, True)
In other words, while calling adapt directly would allow for any adapter;
using the 'Static Typing' short-cut one would be asking for adapters
which are both stateless and lossless. Since __conform__ and __adapt__
would sprout two new arguments, it would make those writing adapters
think a bit more about the kind of adapter that they are providing.
Furthermore, perhaps composite adapters can be automatically generated from 'transitive' adapters (that is, those which are both stateless and lossless). But adaptations which were not stateless and lossless would not be used (by default) in an automatic adapter construction.
Your thoughts?
In some cases, such as when you plan to consume the whole thing in one function call, you wouldn't care so much if it's stateless.
-bob
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