Casting between tuples

[Simen kjaeraas]

Sean Eskapp <eatingstaples at gmail.com> wrote:

> I have a variable of type TypeTuple!(int, int), and I want to convert  
> all its
> elements into a variable of type TypeTuple!(string, string). Is there a  
> way to
> do this? Using a loop fails compilation with "Error: Integer constant
> expression expected instead of i".

Just to be sure, you want something( TypeTuple!(int, int) ) to yield
TypeTuple!( TypeTuple!(string, string), TypeTuple!(string, string) )?

This could be done by means of std.traits' staticMap in conjunction with
a custom template:

template replace( T ) {
     alias TypeTuple!(string, string) replace;
}

alias staticMap!( replace, TypeTuple!( int, int ) ) myNewTuple;
static assert( myNewTuple.stringof == TypeTuple!( TypeTuple!(string,  
string), TypeTuple!(string, string) ).stringof );

> I'd also like to be able to convert from arrays of base classes (static  
> size)
> to TypeTuples of derived classes. "static for" doesn't work either. Is  
> there a
> way to do this.. without a recursive template function?

Not that I know of. Recursive templates are fun, though.

-- 
Simen