Where is CASE?????

[David Bolen]

Larry Smith <larry at smith-house.org> writes:

> Case statements can be modelled with if-else chains
> but they are not the same internally.  Case statements
> are usually compiled as jump tables, rather than as a
> series of if-elses.  This is hugely faster than if-else
> on average.

It's also what often restricts the case statements to integral values
within some range, and the compilation can be less efficient if your
values are sparsely spread over a very large range (in some cases the
compiler may even end up with the same code as an if-else chain).

But in such a case (lookups), dictionaries in Python are very
efficient for lookups and can offer similar performance advantages,
which still being generic in terms of what is being looked up.

> However, in Guido's defense, I will also point out the
> primary use of case statements is to select alternatives
> based on a type flag - which is not needed in an object
> oriented language.

Well, either that, or keeping the list of alternatives in the
dictionary keyed by the type flag is a nice fit.

--
-- David
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