Algorithm.h

Header

#include "react/Algorithm.h"

Summary

Contains various reactive operations to combine and convert signals and events.

• Functions
  • Iterate
  • Hold
  • Snapshot
  • Monitor
  • Pulse
  • OnChanged
  • OnChangedTo

Functions

Synopsis

namespacereact
{
// Iteratively combines signal value with values from event stream
Signal<D,S> Iterate(const Events<D,E>& events, V&& init, F&& func);
Signal<D,S> Iterate(const Events<D,E>& events, V&& init,
const SignalPack<D,TDepValues...>& depPack, FIn&& func);
// Hold the most recent event in a signal
Signal<D,T> Hold(const Events<D,T>& events, V&& init);
// Sets signal value to value of target when event is received
Signal<D,S> Snapshot(const Events<D,E>& trigger, const Signal<D,S>& target);
// Emits value changes of target signal
Events<D,S> Monitor(const Signal<D,S>& target);
// Emits value of target signal when event is received
Events<D,S> Pulse(const Events<D,E>& trigger, const Signal<D,S>& target);
// Emits token when target signal was changed
Events<D,Token> OnChanged(const Signal<D,S>& target);
// Emits token when target signal was changed to value
Events<D,Token> OnChangedTo(const Signal<D,S>& target, V&& value);
}

Iterate

Syntax

// (1)template
<
typename D,
typename E,
typename V,
typename F,
typename S = decay<V>::type
>
Signal<D,S> Iterate(const Events<D,E>& events, V&& init, F&& func); // (2)template
<
typename D,
typename E,
typename V,
typename F,
typename ... TDepValues,
typename S = decay<V>::type
>
Signal<D,S> Iterate(const Events<D,E>& events, V&& init,
const SignalPack<D,TDepValues...>& depPack, F&& func); 

Semantics

(1) Creates a signal with an initial value v = init.

• If the return type of func is S: For every received event e in events, v is updated to v = func(e,v).

• If the return type of func is void: For every received event e in events, v is passed by non-cost reference to func(e,v), making it mutable. This variant can be used if copying and comparing S is prohibitively expensive. Because the old and new values cannot be compared, updates will always trigger a change.

(2) Similar to (1), but the synchronized values of signals in depPack are passed to func as additional arguments. Changes of signals in depPack do not trigger an update - only received events do.

The signature of func should be equivalent to:

• (1a) S func(const E&, const S&)
• (1b) void func(const E&, S&)
• (2a) S func(const E&, const S&, const TDepValues& ...)
• (2b) void func(const E&, S&, const TDepValues& ...)

Graph

(1a)

(2a)

Hold

Syntax

template
<
typename D,
typename V,
typename T = decay<V>::type
>
Signal<D,T> Hold(const Events<D,T>& events, V&& init);

Semantics

Creates a signal with an initial value v = init. For received event values e1, e2, ... eN in events, it is updated to v = eN.

Snapshot

Syntax

template
<
typename D,
typename S,
typename E
>
Signal<D,S> Snapshot(const Events<D,E>& trigger, const Signal<D,S>& target);

Graph

Semantics

Creates a signal with value v = target.Value(). The value is set on construction and updated only when receiving an event from trigger.

Monitor

Syntax

template
<
typename D,
typename S
>
Events<D,S> Monitor(const Signal<D,S>& target);

Semantics

When target changes, emit the new value e = target.Value().

Graph

Pulse

Syntax

template
<
typename D,
typename S,
typename E
>
Events<D,S> Pulse(const Events<D,E>& trigger, const Signal<D,S>& target);

Semantics

Creates an event stream that emits target.Value() when receiving an event from trigger The values of the received events are irrelevant.

Graph

OnChanged

Syntax

template
<
typename D,
typename S
>
Events<D,Token> OnChangedTo(const Signal<D,S>& target);

Semantics

Creates a token stream that emits when target is changed.

OnChangedTo

Syntax

template
<
typename D,
typename V,
typename S = decay<V>::type
>
Events<D,Token> OnChangedTo(const Signal<D,S>& target, V&& value);

Parameters

Creates a token stream that emits when target is changed and target.Value() == value.

V and S should be comparable with ==.