Comma seperated string list to std::list<int>

#include <iostream>
#include <string>
#include <sstream>
#include <list>

bool isSeperator(char c);
bool isNumber(char c);

int main()
{
    std::string input; // Input that gets used in each part of the main function.
    std::string buffer; // A buffer meant to help process the input.

    std::cout << "Please enter a bunch of numbers seperated with commas." << std::endl;
    std::getline(std::cin, input);

    // Remove non seperators or numbers
    buffer = input;
    input = "";
    for( char c : buffer )
    {
        if( isNumber(c) or isSeperator(c) )
        {
            input.push_back(c);
        }
    }

    // Create list with numbers in string format.
    std::list<std::string> str_numbers;
    buffer = "";
    for( char c : input )
    {
        if( isNumber(c) )
            buffer.push_back(c);

        if( isSeperator(c) )
        {
            if(buffer.size() > 0)
            {
                str_numbers.push_back(buffer);
                buffer = "";
            }
        }
    }

    // Convert string numbers into int numbers.
    std::list<int> int_numbers;
    for( std::string str : str_numbers )
    {
        int num;
        std::istringstream ss(str);
        ss >> num;
        int_numbers.push_back(num);
    }

    // Print the numbers
    for( int num : int_numbers )
        std::cout << num << std::endl;
}


bool isSeperator(char c)
{
    if(c == ',')
        return true;

    if(c == ';')
        return true;

    if(c == '&')
        return true;

    return false;
}

bool isNumber(char c)
{
    return (c>='0' && c<='9');
}