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From: Beman Dawes (bdawes_at_[hidden])
Date: 2001-03-02 16:28:11

At 12:56 PM 3/2/2001 -0800, Neal Fachan wrote:

>We noticed you don't include a hash_map template in the
>Boost libraries. We assume this is because every STL
>implementation we can find includes their own hash_map.

No one has submitted one. In fact, I know of one implementor who is
thinking of submitting one to Boost so we may have one someday.

>Unfortunately, none of these hash_map implementations are

That's true, although for many practical purposes they are often close
enough to be used interchangeably.

>We have portable software which uses the native vendor STL
>on all platforms, so this makes using vendors' hash_maps
>What would you advise us to do? We are leaning towards
>taking SGI STL (STLPort)'s hash_map, but putting it into
>it's own quarantined namespace.

What some of the Boost code does is fall back on std::map if not hash_map
is present.

Another thing you might want to do is measure the speed difference between
a hash_map and a std::map in your application. In many applications the
speed difference will not be enough to worry about, or even
detect. Remember, too, hash_map performance may degrade badly on some
platforms. A std::map may be a considerably safer bet.


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