Question

I’m doing a main.cpp to test my implementation of a sparse matrix, where I create two const_iterators:

SparseMatrix<double>::const_iterator a,b;
a=mata.begin(); //mata previously created as SparseMatrix<double>
b=mata.end();
... //code goes on

The problem is that it doesn’t call begin and end (it doesn’t even do the initial cout), but if I create two iterators it works.
Here’s how I implemented begin and end for const_iterators.

const_iterator begin() const
{
    cout<<"Begin"<<endl;
    int minr=minRow();
    int minc=minCol(findRow(minr));
    mcol * mc=findCol(findRow(minr),minc);
    const_iterator x;
    if(mc!=NULL)
    {
        T* dato=&(mc->data);
        x= const_iterator(genElement(minr,minc,dato));
    }
    else
    {
        x=const_iterator(NULL);
    }
    x.setSM(const_cast<SparseMatrix<T>*>(this));
    return x;
}

const_iterator end() const
{
    cout<<"End"<<endl;
    const_iterator x= const_iterator(NULL);
    x.setSM(const_cast<SparseMatrix<T>*>(this));
    return x;
}

A strange thing I noticed is that if I create two const_iterators inside a SparseMatrix’s class method, they work.

Answer 1

As you say, “mata [sic] previously created as SparseMatrix<double>“, but your begin and end that you show are marked const. For those const member functions to be called, the object meta must be const, else the non-const versions of begin and end will be called.