New methods and functions in Typed_array

[Ngoguey42]

Follow-up on #969

• Add getInt16 do dataView
• Add slice to typedArray and arrayBuffer
• Add slice_toEnd to typedArray and arrayBuffer
• Add *fromGenarray and toGenarray functions

[hhugo]

Thanks for your contribution.
I wonder if we should organize and name theses new functions a bit differently.
Also, do you have any preference between Genarray and Array1 ? I suspect Array1 will be more convenient to use, but you might have a different use-case in mind ..

What do you think about introducing a new sub module like

module Bigarray : sig
  val of_int8_signed : (int, int8_signed_elt, c_layout) Bigarray.Array1.t -> int8Array t
  val to_int8_signed : int8Array t -> (int, int8_signed_elt, c_layout) Bigarray.Array1.t
  val of_int8_unsinged : (int, int8_unsigned_elt, c_layout) Bigarray.Array1.t -> int8Array t
  val to_int8_unsigned : int8Array t -> (int, int8_unsigned_elt, c_layout) Bigarray.Array1.t
  ...
end

[Ngoguey42]

Array1 instead of Genarray, one or the other I don't really mind. A Genarray.t has the advantage of being also the ndarray in Owl. Your call.

About the naming, since the Bigarray module is all about GADT i figured it was possible to create two generic from_genarray to_genarray functions. In my latest commit I have pushed an implementation of it and some unit tests. It implies some breaking changes.

In the implementation i had to:

• get rid of the _content_type_ method that seem unused,
• remove ##set_fromArray and replace it with ##set_fromIntArray and ##set_fromFloatArray,
• use locally abstract type in the set/get/unsafe_get methods. When those are used with a int32Array or a uint32Array: int32 is the scalar type instead of int.

I can always roll back to the previous implementation if needed.

[hhugo]

Thanks.
I would prefer to not extend the scope of this PR too much.
Can you revert the three following changes

In the implementation i had to:

• get rid of the _content_type_ method that seem unused,
• remove ##set_fromArray and replace it with ##set_fromIntArray and ##set_fromFloatArray,
• use locally abstract type in the set/get/unsafe_get methods. When those are used with a
  int32Array or a uint32Array: int32 is the scalar type instead of int.

• The first one is tracked TypedArray question #971
• The second and third change could be discussed as part of another PR.

[Ngoguey42]

Okey. Should the former bigarray/typed_array conversions still be included in that PR? They would not make sense alongside a polymorphic implementation introduced in another PR.

[hhugo]

Why is that ? I think I'm missing something ..

[Ngoguey42]

In the latest commit (1a8b1d2), I was able to replace the 14 functions (int8Array_fromGenarray, int8Array_toGenarray, int16Array_fromGenarray, etc....) by those two: from_genarray and to_genarray.

Those 3 changes are mandatory for the from_genarray/to_genarray implementation

• get rid of the _content_type_ method that seem unused,
• remove ##set_fromArray and replace it with ##set_fromIntArray and ##set_fromFloatArray,
• use locally abstract type in the set/get/unsafe_get methods. When those are used with a int32Array or a uint32Array: int32 is the scalar type instead of int.

Reverting those 3 changes means bringing back the 14 previous functions.

Sorry if I wasn't clear.

[hhugo]

I don't understand/see why there are mandatory

[hhugo]

To be clear, I'd like to keep from_genarray/to_genarray in this PR and don't see why the 3 other changes are mandatory consequences.

[Ngoguey42]

In method _content_type_ : 'b, 'b was the polymorphic variant type that is now gone in that implementation.

On master the 'a of class type ['a, 'b] typedArray is either an int or a float. It is actually used in only those 4 functions:

method set_fromArray : 'a js_array t -> int -> unit meth
val set : ('a, 'b) typedArray t -> int -> 'a -> unit
val get : ('a, 'b) typedArray t -> int -> 'a optdef
val unsafe_get : ('a, 'b) typedArray t -> int -> 'a

In order to be compatible with Bigarray,

type int32Array = (int, [ `Int32 ]) typedArray
type uint32Array = (float, [ `Uint32 ]) typedArray

should now be:

type int32Array = (int32, Bigarray.int32_elt) typedArray
type uint32Array = (int32, Bigarray.int32_elt) typedArray

It means that 'a can now also be an int32, but the 4 functions above are not compatible with it and should be changed.

I chose to replace the those 4 functions with 8 non-polymorphic ones (set_fromIntArray/set_float/etc...), and I could mostly ensure the backward compatibility of set/get/unsafe_get using locally abstract types.

[hhugo]

but the 4 functions above are not compatible

I'm still missing something, why would int32 be problematic ?

[Ngoguey42]

You are right, it works like a charm. It wrongly expected the int32 to be an opaque ocaml object, but I just discovered that it is implemented as a javascript number, like int and float. I just reverted those 4 functions.

[hhugo]

close #971

[hhugo]

One issue is that we can now call set_fromTypedArray mixing uint32 and int32 typed array.
But it seems fine.