[m-rev.] New library module: default_map.m

[Fergus Henderson]

On 10-Jul-2001, Ralph Becket <rbeck at microsoft.com> wrote:
> I've needed something like this often enough that I think it should go
> in the standard library.
...
> Extend the library with a new map/2 variant that supports default values
> for keys that have not otherwise been bound in the map.

Hmm... how about just adding a variant of map__search/map__lookup
that takes a default?

E.g.

	map__lookup_with_default(Map, Key, Default) =
		(if map__search(Map, Key, Val) then Val else Default).

I've needed map__lookup_with_default often enough, but I don't think I've ever
needed to store the default in the map.

(Maybe you can think of a more concise name.)

-- 
Fergus Henderson <fjh at cs.mu.oz.au>  |  "I have always known that the pursuit
The University of Melbourne         |  of excellence is a lethal habit"
WWW: <http://www.cs.mu.oz.au/~fjh>  |     -- the last words of T. S. Garp.
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