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August 18, 2008
generic array functions and vector operations
I wanted to test out array operations and create some nice generic functions 
for dealing with vectors. One function is defined as

A[n] lerp(A, uint n)(A t, A[n] a, A[n] b)
{
   return a[] + t * (b[] - a[]);
}

It looks pretty elegant with array operations, but I can't return a static 
array. Is this a bug or missing feature and if not how might one get similar 
elegant syntax without sacrificing efficiency?

I'm not sure the "uint n" part is even valid, but it made sense as it is 
allowed in templates in general.

How would you define and deal with vectors in D?

Bent
August 18, 2008
Re: generic array functions and vector operations
"Bent Rasmussen" wrote
>I wanted to test out array operations and create some nice generic 
>functions for dealing with vectors. One function is defined as
>
> A[n] lerp(A, uint n)(A t, A[n] a, A[n] b)
> {
>    return a[] + t * (b[] - a[]);
> }
>
> It looks pretty elegant with array operations, but I can't return a static 
> array. Is this a bug or missing feature and if not how might one get 
> similar elegant syntax without sacrificing efficiency?

missing feature.  It is a (commonly annoying) limitation of the D spec.

To get around it, you can return a struct with the array inside.

struct StaticArray(T, uint n)
{
  T[n] value;
}

StaticArray!(A, n) lerp(A, uint n)...

-Steve
August 18, 2008
Re: generic array functions and vector operations
"Steven Schveighoffer" <schveiguy@yahoo.com> skrev i meddelelsen 
> missing feature.  It is a (commonly annoying) limitation of the D spec.
> 
> To get around it, you can return a struct with the array inside.
> 
> struct StaticArray(T, uint n)
> {
>   T[n] value;
> }
> 
> StaticArray!(A, n) lerp(A, uint n)...

That's what I figured as well. It's an ugly solution syntax-wise though,
but as the beautiful way is impossible, I suppose it is beautiful for
all practical purposes :-)

It just takes away some of the elegance of array/vector operations in
D as far as I'm concerned.

But I do have a modified struct-based vector implementation inspired
by work done by others here on the forum. That'll have to do until
then.

By the way: Is there a way to vote for features in D? :-)

And where might this get fixed? In D2 and D1 or only in D2?
I want to use D2 but my understanding is that DSSS or is that
Derelict, or both, only supports D1.

Best regards

Bent

> -Steve 
> 
>
August 18, 2008
Re: generic array functions and vector operations
Bent Rasmussen wrote:
> I wanted to test out array operations and create some nice generic 
> functions for dealing with vectors. One function is defined as
> 
> A[n] lerp(A, uint n)(A t, A[n] a, A[n] b)
> {
>    return a[] + t * (b[] - a[]);
> }

Just write it as:

A[] lerp(A)(A t, A[] a, A[] b)
  ...
August 18, 2008
Re: generic array functions and vector operations
"Walter Bright" wrote
> Bent Rasmussen wrote:
>> I wanted to test out array operations and create some nice generic 
>> functions for dealing with vectors. One function is defined as
>>
>> A[n] lerp(A, uint n)(A t, A[n] a, A[n] b)
>> {
>>    return a[] + t * (b[] - a[]);
>> }
>
> Just write it as:
>
> A[] lerp(A)(A t, A[] a, A[] b)
>   ...

What if you just wanted to use static arrays for the non-heap performance 
benefits (and value semantics)?

-Steve
August 19, 2008
Re: generic array functions and vector operations
As Steven writes, I'd prefer optimal efficiency (who wouldn't). Of course in 
a transitional phase dynamic arrays offer the compelling advantage of a 
smooth migration path to static arrays. On the other hand I have no idea 
when or if static array return types will be allowed and so I may as well 
stick with the struct based approach, which have the desired efficiency, 
while "waiting for Cousteau". :-)

Bent

"Walter Bright" <newshound1@digitalmars.com> skrev i meddelelsen 
news:g8cj44$1qmf$2@digitalmars.com...
> Bent Rasmussen wrote:
>> I wanted to test out array operations and create some nice generic 
>> functions for dealing with vectors. One function is defined as
>>
>> A[n] lerp(A, uint n)(A t, A[n] a, A[n] b)
>> {
>>    return a[] + t * (b[] - a[]);
>> }
>
> Just write it as:
>
> A[] lerp(A)(A t, A[] a, A[] b)
>   ...
August 19, 2008
Re: generic array functions and vector operations
I see that the language specification likens tuples to [static] arrays and 
states that it may become possible to return tuples from functions, as well 
as using operators on them. As such, might one imagine a future with vector 
operations on tuples as well? Not that I see any reason to use them over 
static arrays per se - array literals are more straight-forward, at least as 
it stands now.

Bent

"Walter Bright" <newshound1@digitalmars.com> skrev i meddelelsen 
news:g8cj44$1qmf$2@digitalmars.com...
> Bent Rasmussen wrote:
>> I wanted to test out array operations and create some nice generic 
>> functions for dealing with vectors. One function is defined as
>>
>> A[n] lerp(A, uint n)(A t, A[n] a, A[n] b)
>> {
>>    return a[] + t * (b[] - a[]);
>> }
>
> Just write it as:
>
> A[] lerp(A)(A t, A[] a, A[] b)
>   ...
August 19, 2008
Re: generic array functions and vector operations
"Bent Rasmussen" <IncredibleShrinkingSphere@Gmail.com> wrote in message 
news:g8ccrj$1c26$1@digitalmars.com...

> By the way: Is there a way to vote for features in D? :-)
>
> And where might this get fixed? In D2 and D1 or only in D2?
> I want to use D2 but my understanding is that DSSS or is that
> Derelict, or both, only supports D1.

Only in D2.  D1 does not get new features.

And yes, you can vote for features in D, by simply voicing your opinion. 
There is an infinitessimally small (but non-zero) chance that your 
suggestion will make it in.  But returning static arrays is something that 
even Walter has mentioned before, so I wouldn't be surprised if it made it 
in.
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