Ralf Hemmecke <r...@hemmecke.de> writes: [...]
| Whatever the code says, it is not what I think how it should work. I | rather trust the intentions of the original developers and they say in | the Axiom Book > | http://axiom-wiki.newsynthesis.org/uploads/chapter-2.xhtml#sec-2.7 > | A coercion is a special kind of conversion that Axiom is allowed | to do automatically when you enter an expression. Coercions are | usually somewhat safer than more general conversions. The Axiom | library contains operations called coerce and convert. | Only the coerce operations can be used by the interpreter to | change an object into an object of another type unless you explicitly | use a ::. > | For me that means, that only "coerce" functions are allowed to be | inserted automagically. Never "convert". I am not so sure about | "retract" or rather "retractIfCan". The latter are probably necessary to | go back to the most specific domain that an object lives in. > | When I started with Axiom, I got confused by the mere existance of | convert and coerce. They actually seem to be there for the same purpose. | But no, the difference is that the interpreter can use coerce but not | convert. If this distinction is blurred then it makes no sense to have | two different names. A reasonably good mental model of 'coerce' is that it injects a value of one domain into another domain, e.g. you can inject the integer value 1 into the ring of polynomial with integer coefficients without much of computational information loss. On the other hand, there are situations where we want a different representation of a value, but we are willing to accept for a little bit of occasional information loss: that is where 'convert' is most appropriate. The string representation (in base 10) of a DoubleFloat is not an injection as is well known. > | So I am rather in favour of keeping that difference and working towards | a clear distinction. > | As you see above there is a ::. While I worked with Axiom, I never | really thought about its explicit meaning. In Aldor the meaning is | clearly defined. a::X is syntactic sugar for coerce(a)@X. No retract, no | convert. But that is Aldor. In Axiom, it seems that :: can mean what | coerceOrConvertOrRetract says. Can you confirm that your above cited | function is the explicit translation of ::? The Axiom interpreter actually does make the distinction. Apparently, some people don't want that distinction so they have a flag that you can set to tell the interpreter to use 'convert' when it should be using only 'coerce'. | If it is part of the process of inserting coercions to make the types | match, then I'd argue that this should be fixed in favour of a clear | distinction between coerce and convert. > | I know that we somewhat disagree on the "automatic insertion of | coercions in the compiler", but what I just said, all applied to the | interpreter. The compiler should in my opinion never silently insert a | coercion. The compiler is a different story from the interpreter. ------------------------------------------------------------------------------ ThinkGeek and WIRED's GeekDad team up for the Ultimate GeekDad Father's Day Giveaway. ONE MASSIVE PRIZE to the lucky parental unit. See the prize list and enter to win: http://p.sf.net/sfu/thinkgeek-promo _______________________________________________ open-axiom-devel mailing list open-axiom-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/open-axiom-devel
