From: "Harrison, John R" <johnh@ichips.intel.com>
To: "caml-list" <caml-list@inria.fr>
Cc: "Harrison, John R" <johnh@ichips.intel.com>
Subject: RE: [Caml-list] really HO Functions
Date: Thu, 30 Sep 2004 10:30:50 -0700 [thread overview]
Message-ID: <012676D607FCF54E986746512C22CE7D0FE7AD@orsmsx407> (raw)
| I've just had a look through some real programs that I've written and
the
| answer is definitely yes. I use them quite a lot. For >2 they are
mainly 3,
| sometimes 4 and I haven't seen any >4.
I haven't actually checked, but I suspect I'd find something similar.
There may
be an interesting psychological observation to be made here: most people
find
very high-order functions intellectually unmanageable.
Something similar is usually acknowledged in logic with respect to long
quantifier alternations (for all x there exists a y such that for all z,
...).
I believe I once saw a provocative claim by Kreisel that most
mathematical
concepts are in fact only invented in order to hide complicated
quantifier
alternations.
John.
-----Original Message-----
From: owner-caml-list@pauillac.inria.fr
[mailto:owner-caml-list@pauillac.inria.fr] On Behalf Of Jon Harrop
Sent: Wednesday, September 29, 2004 3:31 PM
To: caml-list
Subject: Re: [Caml-list] really HO Functions
On Wednesday 29 September 2004 19:48, Radu Grigore wrote:
> My question is: are there functions of level >= 2 used in practice
> (e.g. (('a -> 'b -> 'a) -> 'a -> 'b list -> 'a) -> 'c)?
I've just had a look through some real programs that I've written and
the
answer is definitely yes. I use them quite a lot. For >2 they are mainly
3,
sometimes 4 and I haven't seen any >4.
> If so, are
> there any typical ones that appear in many applications (maybe not as
> widespread like map & company but at least of comparable usefulness)?
I seem to use them when I write generic functions which are later
specialised.
> One example of a level 2 function (stolen from a recent post by Jon
> Harrop) is this:
> let sum fold = fold (+);;
Funny to think that this function is still state-of-the-art Java and
C++. ;-)
Cheers,
Jon.
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next reply other threads:[~2004-09-30 17:30 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-09-30 17:30 Harrison, John R [this message]
2004-10-04 11:13 ` [Caml-list] Wierd behavior of file reading when tried to start an executable in Ocaml code Andy Yang
2004-10-04 11:28 ` Keith Wansbrough
2004-10-04 12:40 ` skaller
-- strict thread matches above, loose matches on Subject: below --
2004-09-29 20:48 [Caml-list] really HO Functions Jean-Baptiste Rouquier
2004-10-02 5:02 ` Radu Grigore
2004-10-02 6:33 ` John Prevost
2004-10-02 16:44 ` Seth J. Fogarty
2004-09-29 18:48 Radu Grigore
2004-09-29 19:24 ` Jacques Carette
2004-09-29 22:31 ` Jon Harrop
2004-09-29 23:32 ` Marcin 'Qrczak' Kowalczyk
2004-09-30 6:27 ` Diego Olivier Fernandez Pons
2004-09-30 19:27 ` Michal Moskal
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