Hello,

I got a simple vector template :

struct Vector(T, uint N)
{
      alias type T;
      T data[N];
}

And I'd like to call a function like :

void func(V, V.type default_value)(args...);

But this (of course) doesn't work. Is there a simple and nice way
to do this ? (I'm sure there is ;-))

Thanks.

On Wed, Jun 12, 2013 at 11:26:40PM +0200, matovitch wrote:
> Hello,
> 
> I got a simple vector template :
> 
> struct Vector(T, uint N)
> {
>       alias type T;
[...]

This line should read:

	alias type = T;

And it should work as you wanted.


T

-- 
If you look at a thing nine hundred and ninety-nine times, you are perfectly safe; if you look at it the thousandth time, you are in frightful danger of seeing it for the first time. -- G. K. Chesterton

On Wednesday, 12 June 2013 at 21:36:38 UTC, H. S. Teoh wrote:
> On Wed, Jun 12, 2013 at 11:26:40PM +0200, matovitch wrote:
>> Hello,
>> 
>> I got a simple vector template :
>> 
>> struct Vector(T, uint N)
>> {
>>       alias type T;
> [...]
>
> This line should read:
>
> 	alias type = T;
>
> And it should work as you wanted.
>
>
> T

This was a mistake (it's quite late) :

alias T type;

On 06/12/2013 02:26 PM, matovitch wrote:> Hello,
>
> I got a simple vector template :
>
> struct Vector(T, uint N)
> {
>        alias type T;

You later corrected that it should be

  alias T type;

But still, prefer the new syntax over the backward C syntax:

  alias type = T;

>        T data[N];
> }
>
> And I'd like to call a function like :
>
> void func(V, V.type default_value)(args...);

So, that function is already defined and you are trying to call it? How are you calling it? What is the error message?

> But this (of course) doesn't work. Is there a simple and nice way
> to do this ? (I'm sure there is ;-))

It is not clear to me what the purpose is. :)

Ali

To be more precise the code below doesn't compile :

struct Vector(T, uint N)
{
	alias T type;
	enum dimension = N;
	T data[N];
}

void func(V, V.type def_val) (uint i, V v)
{
	if (i < v.dimension) {
		v.data[i] = def_val;
	}
}

void main()
{
	alias Vector!(int, 3) Vec3i;
	Vec3i v;
	func!(Vec3i, 42)(2, v);
}

With the error message :

test.d(8): Error: no property 'type' for type 'V'
test.d(8): Error: V.type is used as a type

On 06/12/2013 02:47 PM, matovitch wrote:
> To be more precise the code below doesn't compile :
>
> struct Vector(T, uint N)
> {
>      alias T type;
>      enum dimension = N;
>      T data[N];
> }
>
> void func(V, V.type def_val) (uint i, V v)
> {
>      if (i < v.dimension) {
>          v.data[i] = def_val;
>      }
> }
>
> void main()
> {
>      alias Vector!(int, 3) Vec3i;
>      Vec3i v;
>      func!(Vec3i, 42)(2, v);
> }
>
> With the error message :
>
> test.d(8): Error: no property 'type' for type 'V'
> test.d(8): Error: V.type is used as a type
>
>

Here is one way:

void func(V, alias def_val) (uint i, V v)
    if (is (typeof(def_val == V.type)))
{
    if (i < v.dimension) {
        v.data[i] = def_val;
    }
}

Ali

On Wednesday, 12 June 2013 at 21:52:46 UTC, Ali Çehreli wrote:
>
> Here is one way:
>
> void func(V, alias def_val) (uint i, V v)
>     if (is (typeof(def_val == V.type)))
> {
>     if (i < v.dimension) {
>         v.data[i] = def_val;
>     }
> }
>
> Ali

Thank you !

matovitch:

> void func(V, V.type def_val) (uint i, V v)
> {
> 	if (i < v.dimension) {
> 		v.data[i] = def_val;
> 	}
> }

I think something like that is not yet possible, but maybe it will be possible later.

Your code has also allowed me to find a new small compiler bug that I have just filed:

http://d.puremagic.com/issues/show_bug.cgi?id=10346

Bye,
bearophile

On 06/12/2013 02:56 PM, matovitch wrote:
> On Wednesday, 12 June 2013 at 21:52:46 UTC, Ali Çehreli wrote:
>>
>> Here is one way:
>>
>> void func(V, alias def_val) (uint i, V v)
>>     if (is (typeof(def_val == V.type)))

Oops. It should be:

    if (is (typeof(def_val) == V.type))

Hmmm. How come the other one worked as well? Because the type of (def_val == V.type) is compiled as bool and since bool is a valid type, 'is' passes.

>> {
>>     if (i < v.dimension) {
>>         v.data[i] = def_val;
>>     }
>> }
>>
>> Ali
>
> Thank you !

Ali