[pypy-dev] List and string in ootypesystem

Antonio Cuni anto.cuni at gmail.com
Tue Apr 4 10:16:32 CEST 2006

Niklaus Haldimann wrote:
> Oops, I didn't intend to invalidate your work. ;) I actually checked
> your user directory yesterday, because you said in an earlier mail that
> you would work on the branch there. But since I didn't see any changes
> related to rlist I assumed you decided to postpone this ...

No, I was working on that but I didn't commit because I wanted to get 
all things working before doing that... I've had some problem fixing all 
various modules that accessed rpython.rlist directly.

> What you did doesn't look so bad, I just looked at it. In general, I'm
> impressed that you found your way around the RTyper so easily. ;) 

Don't worry, it has not been so easy! :-)

> The
> main difference to our work is that you created many new low-level
> operations for the list interface. Since there will also have to be a
> dict and string interface this would lead to an explosion of low-level
> operations. Our approach also makes testing of these data structures at
> a lower level easier (see test_oolist.py and test_oortype.py).

The reason beyond that is that I've found no other way to do this: I 
really wanted to create as few low-level ops as possibile, but I coudn't 
figure out how to do. I try to explain better what I did: my first 
attempt was to provide a low-level operation 'list_lenght' and then 
implement rtype_is_true in terms of 'list_lenght', so I wrote a thing 
like this:

class ListRepr(AbstractListRepr):
     def rtype_len(self, hop):
         v_lst, = hop.inputargs(self)
         return hop.genop('list_len', [v_lst], resulttype=Signed)

     def rtype_is_true(self, hop):
         v_lst, = hop.inputargs(self)
         return hop.gendirectcall(ll_list_is_true, v_lst)

def ll_list_is_true(lst):
     return lst is not None and len(lst) != 0

I hoped that the rtyper was smart enough to convert 'len(lst)' into my 
low-level op 'list_len', but it wasn't: indeed, it generated code that 
called len function for a generic PyObject* and that was not what I wanted.
I tried to copy the implementation of 
lltypesystem.rlist.ll_list_is_true, but I couldn't because that can call 
the ll_lenght() method that I didn't have. Now it has no longer 
importance, but how could I do to get thing working?

ciao Anto

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