Reference documentation for deal.II version Git 497f915867 2021-09-17 22:46:48 +0200
SparseMatrixIterators::Accessor< number, false >::Reference Class Reference

## Public Member Functions

Reference (const Accessor *accessor, const bool dummy)

operator number () const

const Referenceoperator= (const number n) const

const Referenceoperator+= (const number n) const

const Referenceoperator-= (const number n) const

const Referenceoperator*= (const number n) const

const Referenceoperator/= (const number n) const

## Private Attributes

const Accessoraccessor

## Detailed Description

### template<typename number> class SparseMatrixIterators::Accessor< number, false >::Reference

Reference class. This is what the accessor class returns when you call the value() function. The reference acts just as if it were a reference to the actual value of a matrix entry, i.e. you can read and write it, you can add and multiply to it, etc, but since the matrix does not give away the address of this matrix entry, we have to go through functions to do all this.

The constructor takes a pointer to an accessor object that describes which element of the matrix it points to. This creates an ambiguity when one writes code like iterator->value()=0 (instead of iterator->value()=0.0), since the right hand side is an integer that can both be converted to a number (i.e., most commonly a double) or to another object of type Reference. The compiler then complains about not knowing which conversion to take.

For some reason, adding another overload operator=(int) doesn't seem to cure the problem. We avoid it, however, by adding a second, dummy argument to the Reference constructor, that is unused, but makes sure there is no second matching conversion sequence using a one-argument right hand side.

The testcase oliver_01 checks that this actually works as intended.

Definition at line 220 of file sparse_matrix.h.

## ◆ Reference()

template<typename number >
 SparseMatrixIterators::Accessor< number, false >::Reference::Reference ( const Accessor< number, false > * accessor, const bool dummy )

Constructor. For the second argument, see the general class documentation.

## ◆ operator number()

template<typename number >
 SparseMatrixIterators::Accessor< number, false >::Reference::operator number ( ) const

Conversion operator to the data type of the matrix.

## ◆ operator=()

template<typename number >
 const Reference& SparseMatrixIterators::Accessor< number, false >::Reference::operator= ( const number n ) const

Set the element of the matrix we presently point to to n.

## ◆ operator+=()

template<typename number >
 const Reference& SparseMatrixIterators::Accessor< number, false >::Reference::operator+= ( const number n ) const

Add n to the element of the matrix we presently point to.

## ◆ operator-=()

template<typename number >
 const Reference& SparseMatrixIterators::Accessor< number, false >::Reference::operator-= ( const number n ) const

Subtract n from the element of the matrix we presently point to.

## ◆ operator*=()

template<typename number >
 const Reference& SparseMatrixIterators::Accessor< number, false >::Reference::operator*= ( const number n ) const

Multiply the element of the matrix we presently point to by n.

## ◆ operator/=()

template<typename number >
 const Reference& SparseMatrixIterators::Accessor< number, false >::Reference::operator/= ( const number n ) const

Divide the element of the matrix we presently point to by n.

## ◆ accessor

template<typename number >
 const Accessor* SparseMatrixIterators::Accessor< number, false >::Reference::accessor
private

Pointer to the accessor that denotes which element we presently point to.

Definition at line 269 of file sparse_matrix.h.

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