Thanks to you and Basile, who also replied.

I think I now understand that I need to use the more low-level alloc() 
function with the appropriate tag, since there doesn't seem to be a version 
of alloc_array() suitable for doubles.

At the moment my main worry is that I'm allocating new arrays to pass to the 
function faster than the gc can clean them up... I need to find out about 
hanging on to allocated values on the C side of things.

Thanks,
Daniel.

On Saturday 11 January 2003 11:20 pm, Artem Prisyznuk wrote:
> 11.01.03 22:07:51, Daniel Andor <da209@cam.ac.uk> wrote:
> >If I pass a non-array double using copy_double(), it works and I get the
> >correct number on the other side.
> >
> >Any ideas as to where I've gone wrong?
>
> From Caml manual:
>
> ....
> 18.3.3
> Arrays
>
> Arrays of integers and pointers are represented like tuples, that is, as
> pointers to blocks tagged 0. They are accessed with the Field macro for
> reading and the modify function for writing.
>
> Arrays of floating-point numbers (type float array) have a _special,
> unboxed_, more efficient representation. These arrays are represented by
> pointers to blocks with tag Double_array_tag. They should be accessed with
> the Double_field and Store_double_field macros. ....
>
> >Thanks,
> >Daniel.
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