Increased performance of joining signals by a factor of around 5 (#773)

* increased performance of joining signals by a factor of around 5 - this becomes relevant, when joining a 1000 signals and more

* updated changelog

Author: Nikolas Mayr

CHANGELOG.md

@@ -1,6 +1,7 @@
 # master
 *Please add new entries at the top.*
 
+1. Improved performance of joining signals by a factor of around 5. This enables joining of 1000 and more signals in a reasonable amount of time.
 1. Fixed `SignalProducer.debounce` operator that, when started more than once, would not deliver values on producers started after the first time. (#772, kudos to @gpambrozio)
 1. `FlattenStrategy.throttle` is introduced. (#713, kudos to @inamiy)
 1. Updated `README.md` to reflect Swift 5.1 compatibility and point snippets to 6.1.0 (#763, kudos to @Marcocanc)

Sources/Signal.swift

@@ -1680,7 +1680,7 @@ extension Signal {
 					return true
 				}
 
-				_haveAllSentInitial = values.reduce(true) { $0 && !($1 is Placeholder) }
+				_haveAllSentInitial = values.allSatisfy{ !($0 is Placeholder) }
 				return _haveAllSentInitial
 			}
 		}