c++ - Why am I getting this conversion error when I pass a vector by const reference? -

this question has answer here:

• vector iteration loop throwing error? 1 answer

here's short program prints out terms of std::vector object. vector passed in const reference efficiency.

#include <iostream> #include <vector>  using std::vector; using std::cout; using std::endl;  void print_all_terms(const std::vector<int>&);  int main() {   std::vector<int> sequence_1(4, 100);    print_all_terms(sequence_1);    return(0); }  void print_all_terms(const std::vector<int>& sequence) {   (std::vector<int>::iterator = sequence.begin() ;        != sequence.end() ;        ++it) {     std::cout << *it << " ";   }   std::cout << std::endl; } 

however, when run program, error:

error: conversion '__gnu_cxx::__normal_iterator<const int*, std::vector<int, std::allocator<int> > >' non-scalar type '__gnu_cxx::__normal_iterator<int*, std::vector<int, std::allocator<int> > >' requested 

this caused fact iterator it declared std::vector<int>::iterator, resolves to

__gnu_cxx::__normal_iterator<int*, std::vector<int, std::allocator<int> > > 

while begin() function returning object of type

__gnu_cxx::__normal_iterator<const int*, std::vector<int, std::allocator<int> > > 

the difference const in second one. don't see why const should there - yes, variable sequence passed in constant reference, it's reference const, not sequence itself.

you need const_iterator, change loop follows:

for (std::vector<int>::const_iterator = sequence.begin() ;        != sequence.end() ;    ++it) 

if have c++11 compiler, can simplify using auto

for (auto = sequence.begin() ;            != sequence.end() ;  ++it)   

or can use range range loop available c++11

for (auto & val: sequence)  {     std::cout << val << " ";  }