Gabriel Dos Reis <[EMAIL PROTECTED]> writes: > On Mon, 11 Jun 2007, Stephen Wilson wrote: > > | > I guess what I trying to get at is what are the benefits of those > | > additional indirections over simple, hash table representation. > | > | I would imagine that the vast number of lookups would suffice with an > | integer index. Tiny fraction would require higher level keys. > > Lookup with integer index is OK when you have all information at the > same place and at the same time and have a way to enforce its > semantics. Currently, Spad is such that one needs to have all > the information when constructing the vtable but there is no means > to enforce consistency. Going to a world with "extend" makes > the problem even more accute.
If the vtable can be interrogated with a variety of keys, allowing useful mapping of elements, I dont see how a hash is any more flexible. Perhaps you could provide an example? > | > | > >From all I can see, the "index" key relies on order declaration which is > a > | > non-started. The scheme "name" key is essentiablly equivalent to using a > hash > | > table. If an extrat indirection is required to get the type, what is he > | > point? > | > | This indirection could certainly be made fast, probably on par with a > | hash. > > How would that be faster than the scheme that uses only one lookup? I didnt say faster, I said on par. Either scheme is O(1), and the constant difference would be small. I suspect the difference in lookup time would become noticable only when everything that can be accomplished using a simple integer index is replaced by a hash lookup. > | I dont think of the integer index as having anything to do with the > | order of declarations. > > Please elaborate on its semantics then. Nothing fancy. Its just a key, no more, no less. [...] I belive for this dicussion to be productive some prototype implementation would be useful as the focus now seems to be on efficiency. Unless you have already explored this alternative, I can write a few functions which exploit the current vtable structure to provide some of the mappings which you require. I hope to clarify my own rusty comprehension of their layout in the process. Perhaps then we could look at the issues involved in more detail. Thanks, Steve _______________________________________________ Axiom-developer mailing list Axiom-developer@nongnu.org http://lists.nongnu.org/mailman/listinfo/axiom-developer
