Re: [Ocaml-lib-devel] Idea with ExtList.fold_right

[John M. S. <sk...@oz...>]

Brian Hurt wrote:

> On Mon, 16 Jun 2003, Nicolas Cannasse wrote:



>I'm treading dangerously close to saying "if 
> you're using fold_right, you're screwing up.  One of List.map, Enum.map, 
> or List.fold_left is what you really want to be using."


It depends on context. Generally I use whatever is easiest to
read and write, becaise generally I am dealing with lists
of 0-10 elements, with 0-3 being 99% of the cases
(number of parameters a function has in a typical program, number
of components in a product type)

Sometimes I have slightly longer lists, for example:
list of all tokens in the program: that's typically in the
1000's. Vyper actually did something like 10 sub-folds over
the input token stream, mainly to get it into a shape that
could be LALR-parsed. Still, matching on the list was
probably more of an issue than tail recursion for the optimising
compiler: the bytecode compiler crashed out of stack space when
one of my iterations wasn't tail rec, but consuming 10 Meg of stack
isn't a big deal for a binary on a single user machine with 64Meg real.

Now, appending one elements to the end of the token list, on the other
hand, would be a disaster. I dun mind a constant number of O(n) operations,
but n log n where n is in the 1000s is a much bigger number .. a resize array
would be much faster.

Ocaml doesn't have one. Nor mutable doubly-linked lists or other
simple data structures that would sometimed be very convenient,
but a pain to define and then redefine in the next project ..

BTW: lost the web site. Please put web site address
in the signature.



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John Max Skaller, mailto:sk...@oz...
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