On Tue, 08 Dec 2009 21:02:44 -0800, Kee Nethery wrote:
> I string together a bunch of elif statements to simulate a switch
>
> if foo == True:
> blah
> elif bar == True:
> blah blah
> elif bar == False:
> blarg
> elif ....
This isn't what would normally be considered a switch (i.e. what C
considers a switch). A switch tests the value of an expression against a
set of constants. If you were writing the above in C, you would need to
use a chain of if/else statements; you couldn't use a switch.
Compiled languages' switch statements typically require constant labels as
this enables various optimisations.
The above construct is equivalent to Lisp's "cond", or guards in some
functional languages.
While switch-like constructs can be implemented with a dictionary,
cond-like constructs would have to be implemented with a list, as there's
no guarantee that the tests are mutually exclusive, so the order is
significant. E.g.
rules = [((lambda (foo, bar): return foo), (lambda: blah)),
((lambda (foo, bar): return bar), (lambda: blah blah)),
((lambda (foo, bar): return not bar), (lambda: blarg)),
...]
for test, action in rules:
if test(foo, bar):
action()
break
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