Re: [Ocaml-lib-devel] ExtArray?

[skaller <sk...@us...>]

On Thu, 2005-11-24 at 16:23 +0000, Amit Dubey wrote:


> I agree: filter implies you're given a container,  then you "filter"
> away some elements, still left with the same type of container.

Impossible for Array[n]. Ocaml Array is bogus type, not encoding
the length (since it is fixed length). See below ..

> Find_all suggests you're just looking for all matching elements.  It
> doesn't suggest any particular data structure.  So, a list is as good
> as anything.

A problem -- finding the length of the list, so as to create
an array next, is very wasteful. Better to return a list AND
the length of the list, then list + length -> Array is fast,
and you can make versions of filter and find_all that create
arrays.

So 3 primitives and 2 derived functions.

>  One worry with a two-pass approach, though, is it might be
> incompatible with find/inclusion functions that contain state (i.e.
> the state might get confused on the 2nd call).

The whole library has this problem ;(


-- 
John Skaller <skaller at users dot sf dot net>
Felix, successor to C++: http://felix.sf.net