How do I remove this error

[Mr_Hep]

error: invalid operands to binary expression (‘std::list::const_iterator’ (aka
‘_List_const_iterator’) and ‘std::list::const_iterator’
(aka ‘_List_const_iterator’))

for (; Li!=Lend; ++Li, ++Ni)

error: cannot increment value of type ‘std::list::const_iterator’ (aka
‘_List_const_iterator’)

for (; Li!=Lend; ++Li, ++Ni)

The part of code:
if (L.size()!=Ne.size()) abort();
std::list::const_iterator Li (L.begin());
std::list::const_iterator Lend(L.end());
std::list::const_iterator Ni (Ne.begin());

for (; Li!=Lend; ++Li, ++Ni) {…}

[ferhue]

@Mr_Hep

std::list::const_iterator Li (L.begin());

Use instead:
std::list::iterator Li (L.begin());

Or see for loop - How to iterate through a list of objects in C++? - Stack Overflow

[Mr_Hep]

Actually this was the part of the code
if (L.size()!=Ne.size()) abort();
std::list double ::const_iterator Li (L.begin());
std::list double ::const_iterator Lend(L.end());
std::list double ::const_iterator Ni (Ne.begin());

for (; Li!=Lend; ++Li, ++Ni) {

I tried what you recommended, but it didn’t work

[ferhue]

Both for Li and Ni, you need to remove the “const” when defining it. You can’t define something as constant, and then change its value (++Li, ++Ni).