C++17 Features

Key C++17 Features

C++17 added powerful features that make code cleaner and more expressive. Compile with -std=c++17.

Structured Bindings

#include <iostream>
#include <map>
#include <tuple>
using namespace std;

int main() {
    // Decompose pair
    map<string,int> scores = {{"Alice",95},{"Bob",82}};
    for (auto& [name, score] : scores) {
        cout << name << ": " << score << endl;
    }

    // Decompose tuple
    auto [x, y, z] = make_tuple(1, 2.5, "hello");
    cout << x << " " << y << " " << z << endl;
    return 0;
}

std::optional

Represents a value that may or may not be present — safer than returning -1 or null:

#include <optional>

optional<int> divide(int a, int b) {
    if (b == 0) return nullopt;
    return a / b;
}

auto result = divide(10, 2);
if (result.has_value())
    cout << "Result: " << *result << endl;  // 5

auto bad = divide(5, 0);
cout << bad.value_or(-1) << endl;           // -1

if with Initializer

map<string,int> m = {{"key", 42}};

if (auto it = m.find("key"); it != m.end()) {
    cout << "Found: " << it->second << endl;
}
// 'it' not visible outside the if

std::filesystem

#include <filesystem>
namespace fs = filesystem;

fs::create_directory("output");
for (const auto& entry : fs::directory_iterator(".")) {
    cout << entry.path() << endl;
}

Summary

• Structured bindings: auto [a, b] = pair — unpack tuples and maps cleanly.
• std::optional: express "value or nothing" without magic sentinel values.
• if (init; cond): scoped variable in if condition.
• std::filesystem: portable file and directory operations.