switchB?

[Fred Janon]

I don't understand what switchB does:

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switchB [top]

switchB(sourceBB) -> Behavior a

sourceBB :: Behavior (Behavior a)

When the value of a time varying value is time varying itself, which is common when dealing DOM objects.

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Any idea?

Thanks

Fred

[Arjun Guha]

I think the filters demo (which is documented in the OOPSLA paper) is
a relatively tame use of switch:

http://www.flapjax-lang.org/demos/index.html#filters

The OOPSLA paper discusses the compiled code, where switchB is
inserted by the compiler. So, check out the library-mode code:

http://www.flapjax-lang.org/try/index.html?edit=filters.html

This expression in particular:

subFilter.liftB(function(x) { return x.pred; }).switchB()};};

subFilter is a behavior (since we're lifting it, it must be a
behavior). Moreover, subFilter is a behavior of objects, x with a
field x.pred, which is itself a behavior.

Do you see why this is problem? Once you understand the problem, I
think switchB will make more sense, since it solves this "behavior
inside a behavior" problem.

Arjun

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