"Hiding" the mixin keyword?

Reiner Pope xxxx at xxx.xxx
Fri Feb 23 15:04:33 PST 2007

I don't think this is possible, but it certainly seems worthwhile to 
support more advanced features through a standard function-call interface.

Andrei has been nagging Walter about this and making suggestions, so I 
suppose we can hope it will be implemented sometime soon.

renoX wrote:
> What I would like is a way to 'hide' the mixin keyword, is-it possible 
> to put into the template so that the result would look like:
> putf!("Should be 31: %d{x+y+1}\n"); ?

I don't think it would be too hard to work out the details. What I can 
think you might need is the following:

  1. The ability to specify that certain parameters in the list must be 
compile-time constants, and the ability to overload by this.
  2. Some kind of interface at the declaration site that specifies that 
the return value of a given function be mixed into the code instead of 
just treated as a value

The first one could look like this:

> RegExpMatch matchRegexp(static char[] compileTimePattern, char[] text){...} // Parses the pattern at compile time
> RegExpMatch matchRegexp(char[] runtimePattern, char[] text) {...} // Parses it at runtime

This would mean a library user wouldn't have to call a different 
function to get the compile-time version than to get the runtime version.

The second would just involve adding some kind of modifier to a template 
declaration, like the following:

> mixin template putf(A...)
> {
>     const char[] putf = ...;
> }
> // Instantiated like:
> putf!("stuff");
> or
> mixin char[] putf(static char[] pattern)
> {
>     ...
>     return generatedCode;
> }
> // Instantiated like:
> putf("pattern %d{foo}");
> // with the return value mixed in

This could also give you cool things, like the ability to mimic tuple's 
compile-time indexing and make your own tuple wrapper:

> struct MyTuple(A...)
> {
>     A data;
>     typeof(A[i]) opIndex(static size_t i)
>     {
>         return data[i];
>     }
> }



More information about the Digitalmars-d-learn mailing list