I have defined new type:
typedef int(* func) (const std::vector<cv::Mat>&, cv::Mat&);
Then I did class member:
std::map< std::string, std::pair<int,func> > functions;
In function, in first line:
pair<funcId,func> functionSet::getRandomFunction() const
{
map<string, pair<int,func>>::iterator it = functions.begin();
std::advance(it, functions.size());
string name = it->first;
func function = it->second.second;
int argumentsNumber = it->second.first;
funcId id = make_pair(argumentsNumber,name);
pair<funcId,func> p = make_pair(id,function);
return p;
}
I got this error:
error: conversion from 'std::map, std::pair&, cv::Mat&)> > ::const_iterator {aka std::_Rb_tree_const_iterator, std::pair&, cv::Mat&)> > >}' to non-scalar type 'std::map, std::pair&, cv::Mat&)> >::iterator {aka std::_Rb_tree_iterator, std::pair&, cv::Mat&)> > >}' requested map>::iterator it = functions.begin();
Your method marked as const, and so this
has type const functionSet*
. Change you first line:
map<string, pair<int,func>>::const_iterator it = functions.begin();
or if your compiler supports C++11 standard:
auto it = functions.cbegin();
Look at the output again:
conversion from
'std::map, std::pair&, cv::Mat&)> >::const_iterator {...}'
to non-scalar type
'std::map, std::pair&, cv::Mat&)> >::iterator {...}'
So it seems that functions
is a const map, its begin()
returns a const iterator, and it cannot be converted into a normal iterator.
The reason it is constant because because getRandomFunction
is a constant member function and therefore it can see the class members as constants.
As you do not modify the map, simply using const_iterator
should solve the problem:
map<string, pair<int,func>>::const_iterator it = functions.begin();
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