
FRP.Reactive.Internal.Reactive  Stability  experimental  Maintainer  conal@conal.net 



Description 
Representation for Reactive and Event types. Combined here,
because they're mutually recursive.
The representation used in this module is based on a close connection
between these two types. A reactive value is defined by an initial
value and an event that yields future values; while an event is given
as a future reactive value.


Synopsis 



Documentation 


Events. Semantically: timeordered list of future values.
Instances:
 Monoid: mempty is the event that never occurs, and e mappend
e' is the event that combines occurrences from e and e'.
 Functor: fmap f e is the event that occurs whenever e occurs,
and whose occurrence values come from applying f to the values from
e.
 Applicative: pure a is an event with a single occurrence at time
Infinity. ef <*> ex is an event whose occurrences are made from
the product of the occurrences of ef and ex. For every occurrence
f at time tf of ef and occurrence x at time tx of ex, ef
<*> ex has an occurrence f x at time tf max tx. N.B.: I
don't expect this instance to be very useful. If ef has nf
instances and ex has nx instances, then ef <*> ex has nf*nx
instances. However, there are only nf+nx possibilities for tf
max tx, so many of the occurrences are simultaneous. If you think
you want to use this instance, consider using Reactive instead.
 Monad: return a is the same as pure a (as usual). In e >>= f,
each occurrence of e leads, through f, to a new event. Similarly
for join ee, which is somehow simpler for me to think about. The
occurrences of e >>= f (or join ee) correspond to the union of the
occurrences (temporal interleaving) of all such events. For example,
suppose we're playing Asteroids and tracking collisions. Each collision
can break an asteroid into more of them, each of which has to be tracked
for more collisions. Another example: A chat room has an enter event,
whose occurrences contain new events like speak. An especially useful
monadbased function is joinMaybes, which filters a Maybevalued
event.
 Constructors   Instances  



Apply a unary function inside an EventG representation.



Apply a unary function inside an EventG representation.



Make the event into a list of futures



Reactive value: a discretely changing value. Reactive values can be
understood in terms of (a) a simple denotational semantics of reactive
values as functions of time, and (b) the corresponding instances for
functions. The semantics is given by the function at :: ReactiveG t a >
(t > a). A reactive value may also be thought of (and in this module
is implemented as) a current value and an event (stream of future values).
The semantics of ReactiveG instances are given by corresponding
instances for the semantic model (functions):
 Functor: at (fmap f r) == fmap f (at r), i.e., fmap f r at
t == f (r at t).
 Applicative: at (pure a) == pure a, and at (s <*> r) == at s
<*> at t. That is, pure a at t == a, and (s <*> r) at t
== (s at t) (r at t).
 Monad: at (return a) == return a, and at (join rr) == join (at
. at rr). That is, return a at t == a, and join rr at t ==
(rr at t) at t. As always, (r >>= f) == join (fmap f r).
at (r >>= f) == at r >>= at . f.
 Monoid: a typical lifted monoid. If o is a monoid, then
Reactive o is a monoid, with mempty == pure mempty, and mappend
== liftA2 mappend. That is, mempty at t == mempty, and (r
mappend s) at t == (r at t) mappend (s at t).
 Constructors   Instances  



Apply a unary function inside the rEvent part of a Reactive
representation.



Apply a unary function inside the future reactive inside a Reactive
representation.



Run an event in the current thread. Use the given time sink to sync
time, i.e., to wait for an output time before performing the action.



Run a reactive value in the current thread, using the given time sink
to sync time.



Run an event in a new thread, using the given time sink to sync time.



Run a reactive value in a new thread, using the given time sink to
sync time. The initial action happens in the current thread.


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