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[Caml-list] tree walking with... specular rec functions? what else?

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  - John Carr
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- Xavier Leroy
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    - Gérard_Huet

Date:	-- (:)
From:	John Carr <jfc@M...>
Subject:	Re: [Caml-list] tree walking with... specular rec functions? what else?


I have a minor comment unrelated to the basic algorithm.

>     ...
>     let rec outer lst =
>         if (List.length lst) == 0 then ()
>         else outer (inner lst [])
>     in
>     ...

In general it is better to test for empty rather than compare the size
of a collection to 0.  With some collections (including lists) testing
for empty takes constant time but computing size takes linear time.

Instead of

	if (List.length lst) == 0 then empty-code else full-code

either of these will be faster:

	if lst == [] then empty-code else full-code

	(match lst with [] -> empty-code | _ -> full-code)

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