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digitalmars.D - generic array functions and vector operations

reply "Bent Rasmussen" <IncredibleShrinkingSphere Gmail.com> writes:
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

 
Aug 18 2008
next sibling parent reply "Steven Schveighoffer" <schveiguy yahoo.com> writes:
"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
Aug 18 2008
parent reply "Bent Rasmussen" <IncredibleShrinkingSphere Gmail.com> writes:
"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 
 
 

Aug 18 2008
parent "Jarrett Billingsley" <kb3ctd2 yahoo.com> writes:
"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.
Aug 18 2008
prev sibling parent reply Walter Bright <newshound1 digitalmars.com> writes:
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) ...
Aug 18 2008
next sibling parent "Steven Schveighoffer" <schveiguy yahoo.com> writes:
"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
Aug 18 2008
prev sibling next sibling parent "Bent Rasmussen" <IncredibleShrinkingSphere Gmail.com> writes:
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) ...

Aug 18 2008
prev sibling parent "Bent Rasmussen" <IncredibleShrinkingSphere Gmail.com> writes:
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) ...

Aug 18 2008