shouting versus dotting

[Don]

Benji Smith wrote:
> Simen Kjaeraas wrote:
>> On Wed, 08 Oct 2008 22:02:18 +0200, Simen Kjaeraas 
>> <simen.kjaras at gmail.com> wrote:
>>
>>> On Mon, 06 Oct 2008 12:39:29 +0200, Benji Smith 
>>> <dlanguage at benjismith.net> wrote:
>>>
>>>> Andrei Alexandrescu wrote:
>>>>> One morning I woke up with the sudden realization of what the 
>>>>> problem was: the shouting.
>>>>
>>>> Here's my (nutty) opinion:
>>>>
>>>> Neither the "!" nor the "." really want to be there. I think the 
>>>> language really *wants* to be using a bare set of parens for 
>>>> templates. Because the language actually wants templates and 
>>>> functions to converge.
>>>>
>>>> Instead of a special-case syntax for templates, and a set of special 
>>>> rules for CTFE, and a whole set of parallel "static" statements (if, 
>>>> else, foreach) and a special compile-type-only type construct 
>>>> (tuples), just let D be D, either at runtime or compile type.
>>>>
>>>> If a function could return a Type, and if that type could be used in 
>>>> a Type Constructor, then you'd have all the magic template sauce 
>>>> you'd need, and templates could happily converge themselves with 
>>>> regular functions.
>>>>
>>>> Hey! I told you it was going to be nutty!!!
>>>>
>>>> <g>
>>>>
>>>> --benji
>>>
>>> That would only work for templated functions, though. What about 
>>> templated types?
>>>
>>
>> Forget I ever let my ass do the thinking. I'd really like to see how 
>> this would look, but I feel it'd make for uglier syntax.
> 
> I don't really know how it would work, but the syntax is easy to imagine:
> 
>    Type Dictionary = HashMap(char[], char[]);
>    Dictionary d = new Dictionary();
> 
> In this case, HashMap is just a function (executable at compile-time 
> through CTFE), which returns a type. Once the type has been returned, 
> objects of that type can be instantiated.
> 
> This idea first occurred to me when CTFE was introduced. I thought to 
> myself "if we can have compile-time function exectuion", why can't we 
> also have "runtime template instantiation"? Why is it only possible to 
> define a new type (or to choose which type) at compile time?
> 
> In languages like Ruby, you can attach new methods to an object at 
> runtime. In .NET, you can generate, compile, and load new bytecode 
> instructions on the fly.
> 
> It's hard to think of cases where you'd really want to construct a new 
> type at runtime. But maybe....automatically generating a library of 
> types by querying a database schema?

It makes sense to construct a new type in CTFE code, though.
That would allow a template to be instantiated inside a CTFE function.
Currently, a template can pass its arguments into a CTFE function, but a 
CTFE function cannot pass its arguments to a template.