• Bruno Medeiros (12/12) Nov 13 2007 I was reading the discussion at
• Chris Miller (7/16) Nov 13 2007 me =
• Jari-Matti =?ISO-8859-1?Q?M=E4kel=E4?= (19/30) Nov 13 2007 You can do all kinds of stuff with types, for example foldr/l, currying,
• Jarrett Billingsley (6/12) Nov 13 2007 This works because a delegate literal is really a reference to an

Bruno Medeiros <brunodomedeiros+spam com.gmail> writes:

I was reading the discussion at 
http://d.puremagic.com/issues/show_bug.cgi?id=1100 , and then it got me 
thinking:

What are the use cases for alias parameters, other than:
* parameters that are templates
* parameters that are variables
?

In particular is there any meaningful use case for:
* parameters that are either variables or types ?


-- 
Bruno Medeiros - MSc in CS/E student
http://www.prowiki.org/wiki4d/wiki.cgi?BrunoMedeiros#D

"Chris Miller" <chris dprogramming.com> writes:

On Tue, 13 Nov 2007 09:12:09 -0500, Bruno Medeiros  =

<brunodomedeiros+spam com.gmail> wrote:

 I was reading the discussion at  =

 http://d.puremagic.com/issues/show_bug.cgi?id=3D1100 , and then it got=

 me  =

 thinking:

 What are the use cases for alias parameters, other than:
 * parameters that are templates
 * parameters that are variables
 ?

 In particular is there any meaningful use case for:
 * parameters that are either variables or types ?

What about something that takes either a constant or a variable,  =

determined by the caller, without code duplication? It is also especiall=
y  =

useful with delegate literals, where this allows inlining.

Jari-Matti =?ISO-8859-1?Q?M=E4kel=E4?= <jmjmak utu.fi.invalid> writes:

Bruno Medeiros wrote:

 I was reading the discussion at
 http://d.puremagic.com/issues/show_bug.cgi?id=1100 , and then it got me
 thinking:
 
 What are the use cases for alias parameters, other than:
 * parameters that are templates
 * parameters that are variables
 ?
 
 In particular is there any meaningful use case for:
 * parameters that are either variables or types ?

You can do all kinds of stuff with types, for example foldr/l, currying,
filter, map etc. These are pretty awesome features in my opinion.

I'm still hoping we could somehow unify the templates and proposed macros in
some way. The undocumented feature Chris mentioned is pretty interesting
indeed:

template foo(alias bar) {
  ...
}

void moose() {
  foo!({ chicken(); });
  ...
}

Since alias accepts only explicitly defined symbols and for some unknown
reason delegate literals, I thought this was a hidden macro system :) It
could possibly inline the delegate but it doesn't currently :| Also there
are interesting places where alias parameters could be used, e.g. operator
overloadings (to avoid extra parameter passing). Extending these could
eliminate many cases where you need to use ugly CTFE&mixin trick.

"Jarrett Billingsley" <kb3ctd2 yahoo.com> writes:

"Jari-Matti Mäkelä" <jmjmak utu.fi.invalid> wrote in message 
news:fhd1pm$dke$1 digitalmars.com...

 Since alias accepts only explicitly defined symbols and for some unknown
 reason delegate literals, I thought this was a hidden macro system :) It
 could possibly inline the delegate but it doesn't currently :| Also there
 are interesting places where alias parameters could be used, e.g. operator
 overloadings (to avoid extra parameter passing). Extending these could
 eliminate many cases where you need to use ugly CTFE&mixin trick.

This works because a delegate literal is really a reference to an 
implicitly-defined nested function.  So you're passing an alias to an 
automatically-generated symbol name.  It works with function literals too:

foo!(function void(){ chicken(); });