[Jython-dev] PySequenceList and fastSequence

[David M. <morley@AI.SRI.COM>]

I am looking through the Jython PyTuple and PyList classes and I have  
a few questions/suggestions:

(1) I notice that each PySequenceList (such as a PyTuple or PyList)  
has an instance of PyObjectList, which has a PyObjectArray, which has  
a PyObject[]. Thus each new PySequenceList requires the allocation of  
an array and three Java objects. This also means that calling  
PySequenceList's pyget method calls PyObjectLists's pyget method,  
which calls PyObjectArray's get method, which accesses the underlying  
array. Shouldn't it be possible to fold all this into PySequenceList,  
so that it has a PyObject[] directly? I presume there is some reason  
why this isn't done, I just don't know what it is.

(2) The fastSequence static method of PySequence trusts the PyList  
and PyTuple __len__ methods to tell the truth about their lengths.  
Would it be possible to introduce a new interface that both PyList  
and PyTuple implement and have fastSequence test for this interface  
rather than PyTuple or PyList? This would allow other, user-defined  
subclasses of PySequence to share this behavior.

(3) Where the fastSequence static method of PySequence is not able to  
return the given sequence, it could test whether the sequence  
implements the List interface and if so, use the toArray method to  
construct a PyObject[] rather than constructing an empty list and  
appending to it.

If any of these suggestions sound reasonable, I would be happy to try  
implementing them myself and submitting patches.

- David