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Bug 1340

Summary: Add operator + to sparse matrix iterator
Product: Eigen Reporter: Valentin Roussellet <val.roussellet>
Component: Core - matrix productsAssignee: Valentin Roussellet <val.roussellet>
Severity: Feature Request CC: chtz, gael.guennebaud, val.roussellet
Priority: Normal Keywords: JuniorJob
Version: 3.3 (current stable)   
Hardware: All   
OS: All   
Bug Depends on:    
Bug Blocks: 814    

Description Valentin Roussellet 2016-11-11 14:45:02 UTC
SparseCompressedBase::InnerIterator has operator++ but no operator += or operator +

There are cases where one may want to advance the operator by N elements. Currently, the only way to do it is with a for loop such as :

for (i = 0; i < N; ++i,++iterator) {}

An addition operator is easy to define within the iterator :

inline InnerIterator& operator+=( _Index i ) { m_id += i; return *this; }
inline InnerIterator operator+( _Index i ) 
    InnerIterator result = *this;
    result += i;
    return result;

Similarly, a substraction operator can be added to ReverseIterator

inline ReverseInnerIterator& operator-=( _Index i ) { m_id -= i; return *this; }
inline ReverseInnerIterator operator-( _Index i ) 
    ReverseInnerIterator result = *this;
    result -= i;
    return result;
Comment 1 Valentin Roussellet 2016-11-11 14:47:35 UTC
with s/_Index/Index or Eigen 3.3, of course.
Comment 2 Gael Guennebaud 2016-11-14 14:37:45 UTC
Why not. Feel free to propose a patch. There are two instances to be updated in Eigen/src/SparseCore/SparseCompressedBase.h and Eigen/src/Core/CoreIterators.h respectively.
Comment 3 Valentin Roussellet 2016-12-28 17:40:23 UTC
I submitted pull request #284 with a proposed patch for this issue
Comment 4 Gael Guennebaud 2017-01-03 09:36:41 UTC
Comment 5 Nobody 2019-12-04 16:29:49 UTC
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