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Date: Wed, 15 Jan 2003 16:10:30 +0100
Subject: Re: [Caml-list] C -> CAML linking: loosing values in arrays??
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Cc: Caml List <caml-list@inria.fr>
To: Daniel.Andor@physics.org
From: Damien Doligez <damien.doligez@inria.fr>
In-Reply-To: <200301111907.51989.da209@cam.ac.uk>
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On Saturday, January 11, 2003, at 08:07 PM, Daniel Andor wrote:

> parameters.  Since it's for numerics, I want to pass arrays of doubles.

>   return alloc_array(make_float,p);

You cannot use alloc_array to return a value of type [float array].
This is because arrays of floating-point numbers are not represented
like the other array types in O'Caml: they are allocated in-line,
without the usual pointer indirection.

You will have to allocate the array with [alloc], then fill in the
elements with [Store_double_field]:

#define NUM_DIMS 4
value make_float_array(double *ds)
{
   int i;
   value res;

   res = alloc (NUM_DIMS*Double_wosize, Double_array_tag);
   for (i=0; i<NUM_DIMS; i++){
     Store_double_field (res, i, ds[i]);
   }
   return res;
}


-- Damien

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