Heirarchical name space allocation /Trees

Okasaki, C. DR EECS Christopher.Okasaki at usma.edu
Fri Apr 2 12:51:17 EST 2004

> Who doesn't get at least a bit uneasy when looking at all the
> in e.g. Edison's code?  Okasaki has written some generic functions,
> they have to be renamed manually in each module.  All for the sake of
> efficiency!  Bertrand Meyer did not propose to handle this via
> without ensuring that the compiler would eliminate all the
> And that was in 1985!

I may be misunderstanding what you are saying here, but I think you are
complaining that Edison has a lot of redundancy because it doesn't use
default definitions.  And I think you are attributing that avoidance of
default definitions to a concern about avoiding indirections.  But
indirections and "efficiency" (in the sense I think you mean) have
nothing to do with it!

The redundancy you are referring to comes from two sources.  First is
the desire for Edison to support *both* the class-based style and
the module-based style of accessing the data structures.  As other
posts in this thread have shown, both styles have their strong
supporters, and I didn't see any reason that the library should
dictate one style over the other.  Because the module-based style
doesn't support inheritance, you have to put in explicit definitions
for every operation, even if many of those definitions are one-liners
that refer to generic functions.

The second source of redundancy is that default definitions are
largely useless for this kind of library.  The problem is that
there is rarely *one* generic function that makes sense as the
default.  Instead, there are often two or three or more functions
that are all equally good candidates to be the default.  So
which one do you choose?  If there is one that is appropriate,
say, 80% of the time, then sure go ahead and make that one the
default.  But if there are three, and each is appropriate about
33% of the time, then I think it is more clear not to have a default,
and have every implementation state explicitly which of the
"defaults" it is using.

-- Chris

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