Re: Re: Functions in programming

[Michael Fourman <michael.fourman@ed.ac.uk>]

Dear Bill,

It's not primarily a matter of efficiency, but rather of expressiveness.

In a lazy language one can define an infinite list, pass it around as
a value, and access particular elements of it "on demand".

This demand-driven computation can be conceptually much cleaner than
trying to carefully plan, in advance, which values should be computed
in what order.

See, for example:

http://www.haskell.org/haskellwiki/Performance/Laziness

http://lua-users.org/wiki/HammingNumbersVariant

Best,

Michael

On 21 Mar 2009, at 16:06, Bill Lawvere wrote:

>
> Thanks for the several interesting replies.
> I think I am learning what "lazy" means, but
> there seems to be embedded in it a presupposition
> that the order in which new expressions are
> introduced in a computation is something that
> one does not carefully plan. It still seems to
> me to be possible that the developing languages
> are partly the legacy of an epoch when computational
> power was qualitatively less than now.
>
> I was especially heartened to see the lack of
> support for St. John's position "in the beginning
> was the word", especially in view of the recent
> attempts by physicists to revive that idealist
> position. Many of us have long instinctively
> believed that language should fit concepts
> and concepts should fit reality.
>
> Bill
>
>
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> F. William Lawvere, Professor emeritus
> Mathematics Department, State University of New York
> 244 Mathematics Building, Buffalo, N.Y. 14260-2900 USA
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