Error while working with copy constructor in c++

Question

#include <iostream>

using namespace std;

class cmplex
{
int a,b;
public:
cmplex(int x,int y){a=x;b=y;cout<<"its inside constructor 1"<<a<<" "<<b<<endl;}
cmplex(int y){a=y;cout<<"its inside constructor 2 "<<a<<endl;}
cmplex(){cout<<"its inside constructor 3"<<endl;}
cmplex(cmplex &c){a=c.a;b=c.b;cout<<"its inside copy constructor 1"<<endl;cout<<a<<b<<endl;}
};
int main()
{
cmplex c1(2,3),c2(2,33);
c1=cmplex(2,3),c2=cmplex(2,33);
cmplex c3=cmplex();//"cmplex c3"
cmplex c4(c2);
return 0;
}
Works fine when line no 18. is replaced with "cmplex c3;"
So why is it showing error if line 18 is set "cmplex c3=cmplex();"
Unable to understand the issue.Thanks

Answer 1

Modify your last overload of the class constructor to take

const cmplex&

instead of

cmplex&

This is because assignment operator cannot take RHS of non-constant references. Similar situation:

void assn(std::string& str){}

int main()
{
assn("hello");
return 0;
}