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[Caml-list] Reading a large text file
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Date: 2004-05-01 (18:25)
From: Charles Forsyth <forsyth@t...>
Subject: Re: [Caml-list] Reading a large text file
>>The short answer is no, because in OCaml (unlike in LISP) lists are
>>immutable.  In LISP terminology, there's no way to 'set cdr' on an
>>OCaml 'cons structure'.  The disadvantage to this is that you can't do
>>certain destructive operations on lists, like you can so easily in
>>LISP.  The advantage is that you can't do certain destructive
>>operations on lists!  In other words, your code is more likely to be
>>bug free.

the concurrent programming language Limbo does much the same,
and has a similar penalty for appending to a list.  nevertheless, it has
advantages as you say, and i thought i'd add that the property
turns out to be quite helpful in concurrent programs, because you
can pass another process the current value of a list (for instance by sending
it on a channel) and be sure it always sees the `right' value.
i've found it particularly useful for lock-free concurrent access to caches
implemented by hash tables (array of list of T), when the cache
acts as a hint (as for instance in DNS implementation).
as you say, you can always program a mutable list when you need one.

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