So, it may be that we've made Num a => Behavior a an instance of Num in
which case this is valid code; I think the definition
a = liftA2 (+) b c
is more instructive. The point is that Behavior is an instance of
Applicative, so we can apply a time-varying function (such as (+) b) to a
time-varying argument (such as c) so that the answer is modified when either
the function or the argument is.
Freddie
2009/6/10 Patai Gergely
Anyway, can you give any implementation of this example using the reactive library? If b and c are signals (or behaviours as they are called in Reactive) carrying Num values of the same type, you can simply say a = b + c, and you're done. Signal a will be updated only when either b or c is updated. Note that this must be understood in the context of laziness, i.e. not a single sum is calculated until a sample of a is requested.
Gergely
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