object
RightFolded2
Value Members
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final
def
!=(arg0: Any): Boolean
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final
def
##(): Int
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final
def
==(arg0: Any): Boolean
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final
def
asInstanceOf[T0]: T0
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def
clone(): AnyRef
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final
def
eq(arg0: AnyRef): Boolean
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def
equals(arg0: Any): Boolean
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def
finalize(): Unit
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final
def
getClass(): Class[_]
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def
hashCode(): Int
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final
def
isInstanceOf[T0]: Boolean
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def
monoid[In, Out, Acc](trans: (Out) ⇒ Acc)(foldfn: (In, Out) ⇒ Out)(implicit arg0: Group[Acc]): RightFolded2Monoid[In, Out, Acc]
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def
monoid[In, Out](foldfn: (In, Out) ⇒ Out)(implicit arg0: Group[Out]): RightFolded2Monoid[In, Out, Out]
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final
def
ne(arg0: AnyRef): Boolean
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final
def
notify(): Unit
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final
def
notifyAll(): Unit
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final
def
synchronized[T0](arg0: ⇒ T0): T0
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def
toString(): String
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final
def
wait(): Unit
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final
def
wait(arg0: Long, arg1: Int): Unit
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final
def
wait(arg0: Long): Unit
Inherited from AnyRef
Inherited from Any
This monoid takes a list of values of type In or Out, and folds to the right all the Ins into Out values, leaving you with a list of Out values, then finally, maps those outs onto Acc, where there is a group, and adds all the Accs up. So, if you have a list: I I I O I O O I O I O the monoid is equivalent to the computation:
map(fold(List(I,I,I),O)) + map(fold(List(I),O)) + map(fold(List(),O)) + map(fold(List(I),O)) + map(fold(List(I),O))
This models a version of the map/reduce paradigm, where the fold happens on the mappers for each group on Ins, and then they are mapped to Accs, sent to a single reducer and all the Accs are added up.