Some more template syntax sugar

Reiner Pope reiner.pope at
Fri Sep 1 03:10:49 PDT 2006

I've thought about this ambiguity and still come to not much more of a 
conclusion. However, a few thoughts:

(just to clarify my naming, let's call the current system (parameters 
without names) nameless parameters, and my suggestion (implicit 
templating) typeless parameters)

1. Nameless parameters are a very small syntactical sugar as opposed to 
typeless parameters, and I assert that we can do without them. Most of 
the time, you should name your parameters anyway, so the caller can have 
a better idea of what they are used for, and if you decide that it is 
just way to much to type, then you can get away with only two more 
characters for each parameter:

   int foo(int, int);


   int foo(int a, int b);

which really isn't much more to type.

2. It would be possible to do a small modification of the typeless 
parameter syntax to make it grammatically distinct from typeless 
parameters. For instance, add a '@' to make it clear:

   auto sqr(@x) {...}

While, on the surface, this seems the rights solution, I think it 
creates a similar mental block as we get with lazy parameters: even though

   foo( {x();} );

is only three characters more than

   foo( x() );

you will get people used to 'proper' lazy evaluation (Smug Lisp Weenies) 
who say that this means D doesn't *really* support it. My point: by 
using the same typeless syntax that dynamically typed languages use, it 
appeals much more to fans of those languages.

I think that an unmodified syntax is the best approach from a niceness 
point of view, and if the language were being designed afresh, I would 
go for that and ban nameless parameters, since I've already said they 
are hardly useful.

However, given that we are not starting afresh, there may be some code 
out there which uses nameless parameters. I would guess that that code 
doesn't appear much, and the only places I can imagine it being is in 
interfaces and in extern declarations. Since interfaces can't have 
templates, this would be flagged as an error at compile-time, making it 
easy to find and solve. For extern declarations, I don't know whether 
templates are permitted, so this *may* cause a problem.

Thoughts, anyone?



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