On 05/27/15 17:47, Idan Arye via Digitalmars-d wrote:
> On Wednesday, 27 May 2015 at 08:14:36 UTC, Kagamin wrote:
>> On Tuesday, 26 May 2015 at 23:47:41 UTC, Dennis Ritchie wrote:
>>> If this proposal is considered, it is required to propose to look
>>> at the implementation of macros in Nemerle. Many believe that it
>>> is in Nemerle macros implemented the most successful compared to
>>> other modern languages. Of course, the most successful macros are
>>> implemented in Lisp, but the syntax of the language is poor :)
>>
>> The problem with declarative macro system is that you would need to learn
>> yet another language. Possibly turing-complete. And a declarative
>> turing-complete language is an overkill both for usage and implementation.
>> Imperative macros get it done in an intuitive way in the existing language.
>
> But D already has such a declarative language - the one used in template
> metaprogramming. I think a macro system that plays well with that template
> metaprogramming sub-language will be really nice. For example, CTFE that
> works like a macro and returns types/aliases:
>
> Auto deduceType(Auto args) {
> // some complex imperative code to deduce the type from the args
> return DeducedType;
> }
>
> struct Foo(T...) {
> deduceType(T) value;
> }
That already works. Eg:
alias deduceType(Args...) = typeof({
// some complex imperative code to deduce the type from the args
import std.range;
return mixin(iota(Args.length).map!q{`Args[`~text(a)~']'}().join("+"));
}());
struct Foo(T...) {
deduceType!(T) value;
}
static assert(is(typeof(Foo!(short, ubyte, bool).value)==int));
What all these proposals seem to be about is:
a) better introspection (ie exposing a (preferably simplified and std) AST)
b) AST injection
c) "better" syntax
d) better "optimizations", meaning skipping the emission of code and data
that is never used at runtime.
artur
