count-lines-transform-2020.cpp

// ref: https://gitlab.com/manning-fpcpp-book/code-examples/-/blob/master/chapter-01/count-lines-transform/main.cpp
#include <iostream>
#include <string>
#include <vector>
#include <unordered_map>
#include <fstream>
#include <algorithm>
#include <iterator>
#include <ranges>

using namespace std::ranges;

/**
 * This function opens a file specified by the filename argument,
 * and counts the number of lines in said file
 */
int count_lines(const std::string &filename)
{
    std::ifstream in(filename);

    // We are creating an iterator over the input stream and
    // passing it to the count algorithm to count the number
    // of newline characters
    return std::count(
        std::istream_iterator<char>(in >> std::noskipws),
        std::istream_iterator<char>(),
        '\n');
}

/**
 * 2020 ver.
 */
auto count_lines_in_files(const std::vector<std::string>& files)
{
    return files | views::transform(count_lines);
}

int main(void)
{
    auto results = count_lines_in_files({"main.cpp", "Makefile"});

    for (const auto &result: results) {
        std::cout << result << " line(s)\n";
    }

    return 0;
}