GroupAggregator< SRC, AGG, GRP > Class Template Reference

#include "lib/iter-explorer.hpp"

Description

template<class SRC, typename AGG, class GRP>
class lib::iter_explorer::GroupAggregator< SRC, AGG, GRP >

Decorator for IterExplorer to group consecutive elements controlled by some grouping value GRP and compute an aggregate value AGG for each such group as iterator yield. The first group is consumed eagerly, each further group on iteration; thus when the aggregate for the last group appears as result, the source iterator has already been exhausted. The aggregate is default-initialised at start of each group and then the computation functor FAGG is invoked for each consecutive element marked with the same grouping value — and this grouping value itself is obtained by invoking the functor FGRP on each source value. All computation are performed on-the-fly. No capturing or reordering of the source elements takes place, rather groups are formed based on the changes of the grouping value over the source iterator's result sequence.

Template Parameters

AGG	data type to collect the aggregate; must be default constructible and assignable
GRP	value type to indicate a group

Note

while groupFun is adapted, the aggFun is not adapted to the source iterator, but expected always to take the value type of the preceding iterator, i.e. *srcIter. This limitation was deemed acceptable (adapting a function with several arguments would require quite some nasty technicalities). The first argument of this aggFun refers to the accumulator by value, and thereby also implicitly defines the aggregate result type.

Warning

the Aggregator AGG must not capture references to upstream internal state, because the overall pipeline will be moved into final location after the initial ctor call.

Definition at line 1025 of file iter-explorer.hpp.

Public Types
using	value_type = meta::RefTraits< AGG >::Value
using	reference = meta::RefTraits< AGG >::Reference
using	pointer = meta::RefTraits< AGG >::Pointer

Public Member Functions
	GroupAggregator ()=default
template<class FGRP , class FAGG >
	GroupAggregator (SRC &&dataSrc, FGRP &&groupFun, FAGG &&aggFun)
bool	checkPoint () const
reference	yield () const
void	iterNext ()

Protected Types
using	SrcValue = meta::ValueTypeBinding< SRC >::value_type
using	Grouping = function< GRP(SRC &)>
using	Aggregator = function< void(AGG &, SrcValue &)>

Protected Member Functions
SRC &	srcIter () const
void	pullGroup ()

Protected Attributes
std::optional< AGG >	agg_ {}
Grouping	grouping_
Aggregator	aggregate_

Constructor & Destructor Documentation

GroupAggregator() [1/2]

template<class SRC , typename AGG , class GRP >

GroupAggregator ( )

default

GroupAggregator() [2/2]

template<class SRC , typename AGG , class GRP >

template<class FGRP , class FAGG >

GroupAggregator ( SRC &&  dataSrc, FGRP &&  groupFun, FAGG &&  aggFun  )

inline

Definition at line 1049 of file iter-explorer.hpp.

References GroupAggregator< SRC, AGG, GRP >::pullGroup().

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Member Typedef Documentation

SrcValue

template<class SRC , typename AGG , class GRP >

using SrcValue = meta::ValueTypeBinding<SRC>::value_type

protected

Definition at line 1031 of file iter-explorer.hpp.

Grouping

template<class SRC , typename AGG , class GRP >

using Grouping = function<GRP(SRC&)>

protected

Definition at line 1032 of file iter-explorer.hpp.

Aggregator

template<class SRC , typename AGG , class GRP >

using Aggregator = function<void(AGG&, SrcValue&)>

protected

Definition at line 1033 of file iter-explorer.hpp.

value_type

template<class SRC , typename AGG , class GRP >

using value_type = meta::RefTraits<AGG>::Value

Definition at line 1041 of file iter-explorer.hpp.

reference

template<class SRC , typename AGG , class GRP >

using reference = meta::RefTraits<AGG>::Reference

Definition at line 1042 of file iter-explorer.hpp.

pointer

template<class SRC , typename AGG , class GRP >

using pointer = meta::RefTraits<AGG>::Pointer

Definition at line 1043 of file iter-explorer.hpp.

Member Function Documentation

checkPoint()

template<class SRC , typename AGG , class GRP >

bool checkPoint ( ) const

inline

Definition at line 1060 of file iter-explorer.hpp.

References GroupAggregator< SRC, AGG, GRP >::agg_.

yield()

template<class SRC , typename AGG , class GRP >

reference yield ( ) const

inline

Definition at line 1066 of file iter-explorer.hpp.

iterNext()

template<class SRC , typename AGG , class GRP >

void iterNext ( )

inline

Definition at line 1072 of file iter-explorer.hpp.

References GroupAggregator< SRC, AGG, GRP >::agg_, GroupAggregator< SRC, AGG, GRP >::pullGroup(), and GroupAggregator< SRC, AGG, GRP >::srcIter().

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srcIter()

template<class SRC , typename AGG , class GRP >

SRC & srcIter ( ) const

inlineprotected

Definition at line 1083 of file iter-explorer.hpp.

Referenced by GroupAggregator< SRC, AGG, GRP >::iterNext(), and GroupAggregator< SRC, AGG, GRP >::pullGroup().

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pullGroup()

template<class SRC , typename AGG , class GRP >

void pullGroup ( )

inlineprotected

Note

establishes the invariant: source has been consumed up to the beginning of next group

Definition at line 1091 of file iter-explorer.hpp.

References GroupAggregator< SRC, AGG, GRP >::agg_, GroupAggregator< SRC, AGG, GRP >::aggregate_, GroupAggregator< SRC, AGG, GRP >::grouping_, and GroupAggregator< SRC, AGG, GRP >::srcIter().

Referenced by GroupAggregator< SRC, AGG, GRP >::GroupAggregator(), and GroupAggregator< SRC, AGG, GRP >::iterNext().

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Member Data Documentation

agg_

template<class SRC , typename AGG , class GRP >

std::optional<AGG> agg_ {}

protected

Definition at line 1035 of file iter-explorer.hpp.

Referenced by GroupAggregator< SRC, AGG, GRP >::checkPoint(), GroupAggregator< SRC, AGG, GRP >::iterNext(), and GroupAggregator< SRC, AGG, GRP >::pullGroup().

grouping_

template<class SRC , typename AGG , class GRP >

Grouping grouping_

protected

Definition at line 1037 of file iter-explorer.hpp.

Referenced by GroupAggregator< SRC, AGG, GRP >::pullGroup().

aggregate_

template<class SRC , typename AGG , class GRP >

Aggregator aggregate_

protected

Definition at line 1038 of file iter-explorer.hpp.

Referenced by GroupAggregator< SRC, AGG, GRP >::pullGroup().

Inheritance diagram for GroupAggregator< SRC, AGG, GRP >:

Collaboration diagram for GroupAggregator< SRC, AGG, GRP >:

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The documentation for this class was generated from the following file:

• iter-explorer.hpp