#include <iostream>

#include <string>

#include <vector>

#include <algorithm> // for_each

#include <functional> // function

using namespace std;

void example1();

void example2();

void example3();

int main() {

example1();

example2();

example3();

return 0;

}

// C++의 람다식을 설명하기 위한 예제

void example1() {

auto lambda1 = [](const string& a, const string& b) -> bool

{ return a.size() < b.size(); };

int sz = 10;

// auto lambda2 = [sz](const string& a) { return a.size() >= sz; };

// capture list에서 & 사용

auto lambda2 = [&sz](const string& a) { return a.size() >= sz; };

cout << lambda1("abc", "def ghi") << endl;

cout << lambda2("hello") << endl;

sz = 3;

cout << lambda2("hello") << endl;

}

// 람다의 활용예 1번: 템플릿의 인자

void example2() {

vector<string> words;

words.push_back("a");

words.push_back("de");

words.push_back("ghi");

char c = ' ';

ostream& os = cout;

for_each(words.begin(), words.end(),

[&os, c](const string& s) { cout << s << c; });

sort(words.begin(), words.end(),

[](const string& s1, const string& s2) { return s1 > s2; });

for_each(words.begin(), words.end(),

[&os, c](const string& s) { cout << s << c; });

int num = 2;

cout <<

count_if(words.begin(), words.end(),

[num](const string& s) { return s.length() < num; })

<< endl;

}

// 람다의 활용예 2번: 고차원 함수

void example3() {

auto addtwointegers = [](int x) -> function<int(int)> {

return [=](int y) { return x + y; };

};

auto higherorder = [](const function<int(int)>& f, int z) {

return f(z) * 2;

};

auto answer = higherorder(addtwointegers(7), 8);

cout << answer << endl;

}