Jean-Christophe Filliatre wrote:

> - Recursive data-types.  I didn't follow your arguments  about C++ STL
>   versus lists in functional  programming. Of course, lists are almost
>   always bad  data-structures. But  a good functional  programmer does
>   not use lists as data-structures  (a Lisp programmer, may be :-) but
>   rather balanced trees,  Patricia trees, binomial heaps, hash-tables,
>   etc. Moreover, most of  these datatypes are persistent, an essential
>   property  is  several  applications  (whether  in-place  destructive
>   datastructures  require explicit  copies, which  are time  and space
>   consuming). You should read  Chris Okasaki's book "Purely Functional
>   Data Structures".

I have not found a method to implement a  set

with an efficient element removal operation.

To my knowledge, the implementation of set based on balanced tree is efficient for

union, difference etc, but does not seem to be reasonably

efficient for deleting an element. Besides, the tree-based

implementation of set requires that the elements have an ordered type,

it is not clear to me how to extend these techniques

to build a set of unordered elements, say, set of sets.

--
Dennis Gang CHEN    Senior Software Engineer
Motorola Australia Software Centre, Electronic Design Automation
2 Second Avenue, Mawson Lakes, SA 5095, Australia
phone: +61 8 8203 3560,  mailto: Dennis.G.Chen@motorola.com