In article <d4cf71b0050127093664c9bf7b / mail.gmail.com>, Lyle Johnson wrote:
>On Fri, 28 Jan 2005 01:56:24 +0900, Asbjøòn Reglund Thorsen
><asbjoert / ifi.uio.no> wrote:
>
>> I am quite new to extending Ruby, and I have read the README.EXT.
>> I am wondering how to translate (from the code below):
>> "PyList_SetItem($result, i, PyFloat_FromDouble((double) p(i+1)));"
>> Into Extending Ruby syntax.
>
>The (roughly) equivalent code in a Ruby extension would be:
>
>    $result = rb_ary_new2(size);
>    for (int i = 0; i < size; i++)
>        rb_ary_store($result, i, rb_float_new((double) p(i+1)));
>
>Note that in Ruby you construct an Array instance with a certain
>initial size by calling rb_ary_new2(size), and then you set the array
>items by calling rb_ary_store(). Also, the function for constructing a
>Ruby Float object from a C double is rb_float_new().

As an alternative to rb_ary_store(), you can access the buffer underlying
the Array directly:

    $result = rb_ary_new2(size);
    for (int i = 0; i < size; ++i)
    	RARRAY($result)->ptr[i] = rb_float_new((double) p(i+1)));

The latter is faster since it doesn't have to check things like
 - 'Do we need to increase the buffer size'
 - 'Is the buffer shared with another Array'
 - 'Is the Array frozen'
 ...etc.