Hi,

I'd like to write a function for a vector template which basically looks like

struct Vec(T, size_t size) {
  T[size] e;
}

This template has a few properties with very common names like x, y, z, etc. To avoid mistakes I'd like to write a template constraint for UFCS functions so it accepts any instance of the Vec template, but nothing else. Something in the gist of

auto innerProduct(T)(const T v1, const T v2) if(is(T == Vec)) {

}

How can I do this?

Am 13.09.2012 11:46, schrieb Rene Zwanenburg:
> Hi,
>
> I'd like to write a function for a vector template which basically looks
> like
>
> struct Vec(T, size_t size) {
>    T[size] e;
> }
>
> This template has a few properties with very common names like x, y, z,
> etc. To avoid mistakes I'd like to write a template constraint for UFCS
> functions so it accepts any instance of the Vec template, but nothing
> else. Something in the gist of
>
> auto innerProduct(T)(const T v1, const T v2) if(is(T == Vec)) {
>
> }
>
> How can I do this?

I am doing it in gl3n like this: https://github.com/Dav1dde/gl3n/blob/master/gl3n/util.d#L15

(Sorry when I just sent you a private e-mail, I clicked the wrong answer button in thunderbird)

That works, nice trick!

Thanks

On Thursday, 13 September 2012 at 10:09:08 UTC, David wrote:
> Am 13.09.2012 11:46, schrieb Rene Zwanenburg:
>> Hi,
>>
>> I'd like to write a function for a vector template which basically looks
>> like
>>
>> struct Vec(T, size_t size) {
>>   T[size] e;
>> }
>>
>> This template has a few properties with very common names like x, y, z,
>> etc. To avoid mistakes I'd like to write a template constraint for UFCS
>> functions so it accepts any instance of the Vec template, but nothing
>> else. Something in the gist of
>>
>> auto innerProduct(T)(const T v1, const T v2) if(is(T == Vec)) {
>>
>> }
>>
>> How can I do this?
>
> I am doing it in gl3n like this: https://github.com/Dav1dde/gl3n/blob/master/gl3n/util.d#L15
>
> (Sorry when I just sent you a private e-mail, I clicked the wrong answer button in thunderbird)

Rene Zwanenburg:

> How can I do this?

One possible solution:


struct Vec(T, size_t size) {
    T[size] e;
}
void innerProduct(T, size_t n)(const Vec!(T, n) v1,
                               const Vec!(T, n) v2) {}
void main() {
    Vec!(int, 3) v1, v2;
    innerProduct(v1, v2);
}


(While writing it I have found another little compiler bug).

Bye,
bearophile

That's actually quite straightforward. I forgot how well D's type deduction works.

Thanks

On Thursday, 13 September 2012 at 11:01:18 UTC, bearophile wrote:
> Rene Zwanenburg:
>
>> How can I do this?
>
> One possible solution:
>
>
> struct Vec(T, size_t size) {
>     T[size] e;
> }
> void innerProduct(T, size_t n)(const Vec!(T, n) v1,
>                                const Vec!(T, n) v2) {}
> void main() {
>     Vec!(int, 3) v1, v2;
>     innerProduct(v1, v2);
> }
>
>
> (While writing it I have found another little compiler bug).
>
> Bye,
> bearophile