How to name algorithm in c++ for process items in collection which can add or remove items?

Question

I search for some std:: algorithm but failed. I want to process items from input iterator til last iterator and write output into out iterator. Note output can be less or more then input stream. So I write example to show what exactly I need:

#include <iomanip>
#include <iostream>
#include <iterator>
#include <string>
#include <string_view>

void some_algorithm_name(auto it_beg, auto it_end, auto it_out, auto func)
{
    for (; it_beg != it_end; it_beg++)
    {
        func(*it_beg, it_out);
    }
}

int main(int argc, char** argv)
{
    using namespace std;
    string_view in = "abcdefaa";
    string      out;
    some_algorithm_name(begin(in),
                        end(in),
                        back_inserter(out),
                        [](char ch, auto& out_it)
                        {
                            switch (ch)
                            {
                                case 'a': // duplicate
                                {
                                    *out_it++ = 'a';
                                    *out_it++ = 'a';
                                    break;
                                }
                                case 'b': // skip
                                {
                                    break;
                                }
                                case 'c': // change/transform
                                {
                                    *out_it++ = 'd';
                                    break;
                                }
                                case 'd': // change/transform
                                {
                                    *out_it++ = 'c';
                                    break;
                                }
                                default: // copy
                                {
                                    *out_it++ = ch;
                                }
                            }
                        });

    string expected = "aadcefaaaa";
    cout << "input: " << quoted(in) << endl;
    cout << "output: " << quoted(expected) << (expected == out ? "==" : "!=")
         << quoted(out) << endl;
    return 0;
}

Is any library or framework where I can find such algorithm? Or maybe you can offer some name for it?

Answer 1

One of approaches is to use standard algorithm std::accumulate declared in header <numeric>. For example

#include <iostream>
#include <string>
#include <string_view>
#include <iterator>
#include <numeric>

int main()
{
    std::string_view in = "abcdefaa";
    std::string out;

    auto lambda = []( auto result, auto ch )
    {
        switch (ch)
        {
        case 'a': // duplicate
            result.append( 2, 'a' );
            break;
        case 'b': // skip
            break;
        case 'c': // change/transform
            result += 'd';
            break;
        case 'd': // change/transform
            result += 'c';
            break;
        default: // copy
            result += ch;
            break;
        }

        return  result;
    };

    out = std::accumulate( std::begin( in ), std::end( in ), std::string(), lambda );

    std::cout << "in = " << in << '\n';
    std::cout << "out = " << out << '\n';
}

The program output is

in = abcdefaa
out = aadcefaaaa

I quickly showed one of approaches based on standard algorithms. However it seems there is better to use the old range-based for loop.