aarti_pl wrote:
aarti_pl pisze:
Andrei Alexandrescu pisze:
2. User-defined operators must be revamped. Fortunately Don already
put in an important piece of functionality (opDollar). What we're
looking at is a two-pronged attack motivated by Don's proposal:
http://prowiki.org/wiki4d/wiki.cgi?LanguageDevel/DIPs/DIP7
The two prongs are:
* Encode operators by compile-time strings. For example, instead of
the plethora of opAdd, opMul, ..., we'd have this:
T opBinary(string op)(T rhs) { ... }
The string is "+", "*", etc. We need to design what happens with
read-modify-write operators like "+=" (should they be dispatch to a
different function? etc.) and also what happens with index-and-modify
operators like "[]=", "[]+=" etc. Should we go with proxies? Absorb
them in opBinary? Define another dedicated method? etc.
* Loop fusion that generalizes array-wise operations. This idea of
Walter is, I think, very good because it generalizes and democratizes
"magic". The idea is that, if you do
a = b + c;
and b + c does not make sense but b and c are ranges for which
a.front = b.front + c.front does make sense, to automatically add the
iteration paraphernalia.
(..)
Andrei
I kinda like this proposal. But I would rather call template like below:
T opInfix(string op)(T rhs) { ... }
T opPrefix(string op)(T rhs) { ... }
T opPostfix(string op)(T rhs) { ... }
and allow user to define her own operators (though it doesn't have to
be done now).
I know that quite a few people here doesn't like to allow users to
define their own operators, because it might obfuscate code. But it
doesn't have to be like this. Someone here already mentioned here that
it is not real problem for programs in C++. Good libraries don't abuse
this functionality.
User defined operators would allow easy definition of Domain Specific
Languages in D. I was already writing about it some time ago:
http://www.digitalmars.com/webnews/newsgroups.php?art_group=digitalmars.D&article_id=81026
http://www.digitalmars.com/webnews/newsgroups.php?art_group=digitalmars.D&article_id=81352
BR
Marcin Kuszczak
(aarti_pl)
Of course for opPrefix/opPostfix signatures will be different:
T opPrefix(string op)() { ... }
T opPostfix(string op)() { ... }
Sorry for mistake.
BR
Marcin Kuszczak
(aarti_pl)
I think we'll solve postfix "++" without requiring the user to define
it. Do you envision user-defined postfix operators?
Andrei
