Re: template template parameter

[Caligo]

I should have been more clear, but my actual question is how do I
access the parameters of a template parameter.  My example works, but
I wanted to know if there is a different and perhaps a better of doing
it.

In your example it would look something like this:

struct SomeContainer(T, int x, int y){ }

struct Foo(alias ContainerType){

  // e.g.
  int my_x = ContainerType.x * 2;
  int my_y = ContainerType.y * 2;
}

Re: template template parameter

[Ali Çehreli]

On 03/30/2011 04:32 PM, Caligo wrote:

I have a struct that looks something like this:

struct Box(T, size_t width, size_t height){

alias width width_;
alias height height_;

//do something with a Box of different size
   void Fun( B )(B b){
 // using width and height of b
 B.width_;
 B.height_;
   }
}

auto b1 = Box!(double, 2, 7)();
auto b2 = Box!(double, 3, 4)();
b1.Fun(b2);

I think the technical name for this is template template parameter.
Using the above I'm able to do what I need to do, but is there a
better way?
and should I use alias or enum?


Template template parameter means exactly that: a template parameter is 
itself a template. See ContainerType below:


struct SomeContainer(T)
{
T[] elements;
}

struct SomeOtherContainer(T)
{
struct List(T)
{}

// e.g. this one may use a linked list
List!T elements;
}

struct Foo(alias ContainerType, T)
{
// Instantiate the 'template template parameter'
ContainerType!T member;
}

void main()
{
Foo!(SomeContainer, double) foo1;
Foo!(SomeOtherContainer, int) foo2;
}

ContainerType is a template parameter of Foo and is itself a template.

And 'alias' seems to work...

Ali