Martin Rubey <[EMAIL PROTECTED]> writes: [...]
| Gaby wrote: | | > although it [Axiom] tends to treat operations from add-chains as if they were | > from default categories or default packages (except that add-chains take | > precedence over defaults). So, that implies to me -- given the way defaults | > work -- that domains can see operations overriden if used in add-chains. | > However, newLookupInTable seems to implement that behaviour only when the | > package is a default. I do not know whether it is a bug of feature, but I do | > want a unifrom behaviour (which tends to push the current behaviour toward a | > bug). | | I think I can live with both - and I even agree that the current (and Aldor's) | behaviour is somewhat inconsistent. Note that in aldor, the keyword "default" | is used to introduce default implementations in categories. | | On the practical side, it allows an optimization which I believe is quite | important. Without the optimization, it makes a (big) difference whether in | IIARRAY2 you write (1) | | minRowIndex m == mnRow | minColIndex m == mnCol | | qelt(m,i,j) == | qelt(qelt(m,i - minRowIndex m)$Rep,j - minColIndex m) | | or (2) | | minRowIndex m == mnRow | minColIndex m == mnCol | | qelt(m,i,j) == | qelt(qelt(m,i - mnRow)$Rep,j - mnCol) | | | In fact, I'm not sure what we want. Somehow, default implementations are a | mixed blessing... I sent some time thinking about this issue, pondering pros and cons, looking at the compiler code. My conclusion is that the existing behaviour was a deliberate design choice to mimic `forgetful functors'. E.g., once one decides to reuse a domain to (partially) implement exported operations, all relevant operations are taken from there, The only way to get the `object oriented' feature of virtual functions (or non-static methods, Java parlance) is to use defaults in categories. This is not well (if at all!) explained in the Axiom Book. I can see how this can be limiting in some cases, but I suspect it makes an interesting language design choice. A fundamental question (to me) is: beside optimizations such as the one you want, is there any programming technique that benefit a lot from that? -- Gaby ------------------------------------------------------------------------- This SF.net email is sponsored by the 2008 JavaOne(SM) Conference Don't miss this year's exciting event. There's still time to save $100. Use priority code J8TL2D2. http://ad.doubleclick.net/clk;198757673;13503038;p?http://java.sun.com/javaone _______________________________________________ open-axiom-devel mailing list open-axiom-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/open-axiom-devel
