Hi,

I've been playing around with templates, i'm a newbie in this matter, i created a class template and i want to use it as a type in functions and create arrays of it. Any help please.

Code sample:

module hello;

template Test(alias T)
{
    class Test
    {
        this(){} int x; ...
    }
}

void Foo(Test t){}

static Test[] myarray;

Reply to Karl,

> Hi,
> 
> I've been playing around with templates, i'm a newbie in this matter,
> i created a class template and i want to use it as a type in functions
> and create arrays of it. Any help please.
> 
> Code sample:
> 
> module hello;
> 
> template Test(alias T)
> {
> class Test
> {
> this(){} int x; ...
> }
> }
> void Foo(Test t){}
> 
> static Test[] myarray;
> 

void Foo(Test!(somthingToAlias) { }
static Test!(somthingToAlias)[] myarray;

look for "Explicit Template Instantiation" in

http://www.digitalmars.com/d/template.html

BCS Wrote:

> Reply to Karl,
> 
> > Hi,
> > 
> > I've been playing around with templates, i'm a newbie in this matter, i created a class template and i want to use it as a type in functions and create arrays of it. Any help please.
> > 
> > Code sample:
> > 
> > module hello;
> > 
> > template Test(alias T)
> > {
> > class Test
> > {
> > this(){} int x; ...
> > }
> > }
> > void Foo(Test t){}
> > 
> > static Test[] myarray;
> > 
> 
> void Foo(Test!(somthingToAlias) { }
> static Test!(somthingToAlias)[] myarray;
> 
> look for "Explicit Template Instantiation" in
> 
> http://www.digitalmars.com/d/template.html
> 
> 

Thanks for your reply.

"somthingToAlias" could be anything right? Lets suppose foo.bar1 or foo.bar2. Then "static Test!(foo.bar1)[] myarray;" would create an array only for elements instantiated from foo.bar1 and i couldn't append an element instantiated from foo.bar2, am i wrong?

1) Then how could i create an array for generic instantiated elements?

2) "void Foo(Test!(somthingToAlias) { }", i think something is missing:

- ")".
- A variable name, (correct me if wrong): void Foo(Test!(somthingToAlias)  sta){ }

Thanks in advance.

Karl wrote:
> BCS Wrote:
> 
>> void Foo(Test!(somthingToAlias) { }
>> static Test!(somthingToAlias)[] myarray;
>>
>> look for "Explicit Template Instantiation" in
>>
>> http://www.digitalmars.com/d/template.html
> 
> "somthingToAlias" could be anything right? Lets suppose foo.bar1 or foo.bar2. Then "static Test!(foo.bar1)[] myarray;" would create an array only for elements instantiated from foo.bar1 and i couldn't append an element instantiated from foo.bar2, am i wrong?
> 
> 1) Then how could i create an array for generic instantiated elements?

You could give your template class a non-templated base function, and use that as the type of the array elements.

> 2) "void Foo(Test!(somthingToAlias) { }", i think something is missing:
> 
> - ")".

Yes, he seems to have made a typo there

> - A variable name, (correct me if wrong): void Foo(Test!(somthingToAlias)  sta){ }

Technically the name is optional, but it does come in quite handy when you actually want to *use* the parameter in the function body :).

Frits van Bommel Wrote:

> Karl wrote:
> > BCS Wrote:
> > 
> >> void Foo(Test!(somthingToAlias) { }
> >> static Test!(somthingToAlias)[] myarray;
> >>
> >> look for "Explicit Template Instantiation" in
> >>
> >> http://www.digitalmars.com/d/template.html
> > 
> > "somthingToAlias" could be anything right? Lets suppose foo.bar1 or foo.bar2. Then "static Test!(foo.bar1)[] myarray;" would create an array only for elements instantiated from foo.bar1 and i couldn't append an element instantiated from foo.bar2, am i wrong?
> > 
> > 1) Then how could i create an array for generic instantiated elements?
> 
> You could give your template class a non-templated base function, and use that as the type of the array elements.
> 
> > 2) "void Foo(Test!(somthingToAlias) { }", i think something is missing:
> > 
> > - ")".
> 
> Yes, he seems to have made a typo there
> 
> > - A variable name, (correct me if wrong): void Foo(Test!(somthingToAlias)  sta){ }
> 
> Technically the name is optional, but it does come in quite handy when you actually want to *use* the parameter in the function body :).

Thanks for your reply.

"You could give your template class a non-templated base function, and use that as the type of the array elements."

I didn't understood. A small example please.

Thanks man.

"Karl" <asdf@asdf.com> wrote in message news:fcsokc$2uhn$1@digitalmars.com...

> "You could give your template class a non-templated base function, and use that as the type of the array elements."
>
> I didn't understood. A small example please.

He meant "non-templated base *class*".  So:

class TestBase
{
    // put common methods here
}

class Test(alias T) : TestBase
{
    this()
    {

    }

    int x;

    ...
}

void Foo(TestBase t) {}
static TestBase[] myArray;

Remember that unlike Java or C# generics, D's templates are done all at compile time.  This means that a Test!(int) is just as different from a Test!(float) as an int[] is from a float[].

Jarrett Billingsley wrote:
> "Karl" <asdf@asdf.com> wrote in message news:fcsokc$2uhn$1@digitalmars.com...
> 
>> "You could give your template class a non-templated base function, and
>> use that as the type of the array elements."
>>
>> I didn't understood. A small example please.
> 
> He meant "non-templated base *class*".  So:

Yes I did. I'm not quite sure how I managed to typo 'class' to 'function' though...

"Frits van Bommel" <fvbommel@REMwOVExCAPSs.nl> wrote in message news:fct4r0$hl9$1@digitalmars.com...
>
> Yes I did. I'm not quite sure how I managed to typo 'class' to 'function' though...

It's understandable.  The keys are right next to each other.

Jarrett Billingsley wrote:
> "Frits van Bommel" <fvbommel@REMwOVExCAPSs.nl> wrote in message news:fct4r0$hl9$1@digitalmars.com...
>> Yes I did. I'm not quite sure how I managed to typo 'class' to 'function' though...
> 
> It's understandable.  The keys are right next to each other. 
> 
> 

You have a [class] key on your keyboard!?  ...is that thing available on Amazon?

-- Chris Nicholson-Sauls