examples/cpp/11.cpp at 30ee3e67dcae1f15a46c50a8e2fba1d25a1a7788 · makelinux/examples · GitHub

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/**

@file

@brief C++11

@defgroup CPP11 C++11 examples

https://en.wikipedia.org/wiki/C++11

https://github.com/AnthonyCalandra/modern-cpp-features/blob/master/CPP11.md

static_assert(__cplusplus == 201103, "");

#include <bits/stdc++.h>

#include <signal.h>

#include <unistd.h>

#if __has_include(<version>)

#include <version>

#endif

using namespace std;

/**

@defgroup lang11 Language

void types_11()

{

static_assert(__cpp_decltype, "");

int a;

// https://en.cppreference.com/w/cpp/header/type_traits

decltype(a) b; // https://en.cppreference.com/w/cpp/language/decltype

assert((is_same<decltype(a), decltype(b)>::value));

assert((!is_same<decltype(a), unsigned>::value));

assert((is_same<int, int32_t>::value));

assert((is_same<signed, int32_t>::value));

assert(is_integral<int>::value);

assert(is_integral<bool>::value);

assert(!is_integral<float>::value);

assert(is_pointer<int*>::value);

assert(sizeof(long long) >= 8);

enum class Number { zero,

tree = 3,

four };

Number n = Number::zero;

assert(static_cast<int>(n) == 0);

assert(is_enum<Number>());

}

/// [unique_ptr](https://en.cppreference.com/w/cpp/memory/unique_ptr)

void unique_pounter()

{

int d = 0;

unique_ptr<int> u1;

assert(!u1);

u1.reset(&d);

assert(u1);

*u1 = 1;

assert(d == 1);

unique_ptr<int> u2;

// u2 = u1; - prohibited

int* p1 = u1.get();

u2 = move(u1); // [move](https://en.cppreference.com/w/cpp/utility/move)

assert(u2.get() == p1);

assert(u2);

assert(!u1);

assert(u2.get() == &d);

// must release because d is local

u2.release();

u2.reset(new int(10));

assert(*u2 == 10);

u2.reset(); // deletes int(10)

assert(u2 == nullptr); // [nullptr](https://en.cppreference.com/w/cpp/language/nullptr)

assert(!u2);

}

/// [shared_ptr](https://en.cppreference.com/w/cpp/memory/shared_ptr)

void shared_pointer()

{

shared_ptr<int> s1;

assert(!s1);

assert(!s1.use_count());

auto s2 = make_shared<int>(1);

assert(s2.use_count() == 1);

s1 = s2;

assert(s1.use_count() == 2);

*s1 = 2;

assert(*s1 == *s1.get());

assert(*s2 == 2);

s2 = nullptr; // like s2.reset();

assert(s1.use_count() == 1);

assert(!s2.use_count());

}

/// [weak_ptr](https://en.cppreference.com/w/cpp/memory/weak_ptr)

void weak_pointer()

{

weak_ptr<int> wp;

assert(!wp.lock());

assert(!wp.use_count());

auto sp = make_shared<int>(1);

wp = sp;

assert(*wp.lock() == 1);

}

/**

[new](https://en.cppreference.com/w/cpp/memory/new/operator_new),

[delete](https://en.cppreference.com/w/cpp/memory/new/operator_delete)

void dynamic_memory_11()

{

auto a = new int[3] { 1, 2, 3 };

assert(a[2] == 3);

delete a;

auto as = new string[3] { "1", "2", "3" };

assert(as[2] == "3");

delete[] as; // calls destructors for all members

unique_pounter();

shared_pointer();

weak_pointer();

}

/// func_type - overloaded functions

/// [remove_reference](https://en.cppreference.com/w/cpp/types/remove_reference)

char func_type(const int& x)

{

assert(is_const<typename remove_reference<decltype(x)>::type>::value);

assert(is_lvalue_reference<decltype(x)>::value);

return 'C';

}

char func_type(int& x)

{

assert(is_lvalue_reference<decltype(x)>::value);

return 'L';

}

char func_type(int&& x)

{

assert(is_rvalue_reference<decltype(x)>::value);

return 'R';

}

/// [Forwarding reference](https://en.cppreference.com/w/cpp/language/reference#Forwarding_references)

template <class T>

char func_type_template(T&& x) // x is a forwarding reference

{

// x is not R-value here

assert(func_type(x) != 'R');

// x can be forwarded as R or L value

// https://en.cppreference.com/w/cpp/utility/forward

return func_type(forward<T>(x)); // like func_type((T)(x));

}

/**

[References](https://en.wikipedia.org/wiki/Reference_(C++))

[is_reference](https://en.cppreference.com/w/cpp/types/is_reference),

[ref](https://en.cppreference.com/w/cpp/utility/functional/ref),

[reference_wrapper](https://en.cppreference.com/w/cpp/utility/functional/reference_wrapper)

void references_11()

{

// https://en.cppreference.com/w/cpp/language/reference

assert(is_reference<int&>::value);

// L-value:

assert(is_lvalue_reference<int&>::value);

// R-value

assert(is_rvalue_reference<int&&>::value);

const int c = 1;

int i = 2;

assert(func_type(3) == 'R');

assert(func_type(c) == 'C');

assert(func_type(move(i)) == 'R');

assert(func_type_template(c) == 'C');

assert(func_type_template(i) == 'L');

assert(func_type_template(3) == 'R');

reference_wrapper<int> rw = i;

rw.get() = 3;

assert(i == 3);

auto cr = cref(i);

assert(cr == 3);

}

/**

[direct_initialization](https://en.cppreference.com/w/cpp/language/direct_initialization)

[zero_initialization](https://en.cppreference.com/w/cpp/language/zero_initialization)

[list_initialization](https://en.cppreference.com/w/cpp/language/list_initialization)

[initializer_list](https://en.cppreference.com/w/cpp/utility/initializer_list)

[Member_initialization](https://en.cppreference.com/w/cpp/language/data_members#Member_initialization)

[aggregate_initialization](https://en.cppreference.com/w/cpp/language/aggregate_initialization)

[reference_initialization](https://en.cppreference.com/w/cpp/language/reference_initialization)

void init_11()

{

struct C {

int a, b, c;

};

auto o2 = C { 1, 2, 3 };

C o3 { 1, 2, 3 };

(void)o3;

auto uses_il = [](initializer_list<int> il) {

assert(*il.begin() == 3);

assert(il.size() == 4);

};

uses_il({ 3, 2, 1, 0 });

auto z1 = C();

C z2 = {};

auto z3 = C {};

assert(!z1.a);

assert(!z2.a);

assert(!z3.a);

array<int, 3> a { 1, 2 };

}

/**

Trailing return type

https://en.cppreference.com/w/cpp/language/function

https://www.ibm.com/support/knowledgecenter/en/ssw_ibm_i_73/rzarg/trailing_return.htm

/// https://en.cppreference.com/w/cpp/language/auto

auto auto_int = 1;

// int before(int a) { return a; }

auto trailing_return_type(int a) -> int

{

return a;

}

/// [copy_elision](https://en.cppreference.com/w/cpp/language/copy_elision)

void copy_elision_demo()

{

struct Obj2 {

Obj2* orig = this;

int ballast[4];

};

auto&& o2 = []() { return Obj2(); }();

assert(&o2 == o2.orig);

}

void func_11()

{

class functor {

int y = 1;

public:

int operator()(int a) const

{

return a + y;

}

};

functor ft;

assert(ft(1) == 2);

// https://en.cppreference.com/w/cpp/utility/functional/function

function<int(int)> ft2 = ft;

assert(ft(2) == 3);

return;

// https://en.cppreference.com/w/cpp/utility/functional/bind

auto binded = bind(ft2, 3);

assert(binded() == 5);

copy_elision_demo();

}

static_assert(__cpp_constexpr, "");

/// https://en.cppreference.com/w/cpp/language/constexpr

constexpr int constexpr_factorial(int n)

{

return n <= 1 ? 1 : (n * constexpr_factorial(n - 1));

}

/// https://en.cppreference.com/w/cpp/language/parameter_pack

template <typename T>

T constexpr adder(T v)

{

return v;

}

template <typename T, typename... Args>

T constexpr adder(T first, Args... args)

{

return first + adder(args...);

}

static_assert(adder(1, 2, 3) == 6, "");

static_assert(adder<int>(1, 2, 3) == 6, "");

struct Base11 {

virtual void method1();

virtual void method2();

};

struct Derived11 : Base11 {

void method1() override; ///< [override](https://en.cppreference.com/w/cpp/language/override)

void method2() final; ///< [final](https://en.cppreference.com/w/cpp/language/final)

};

void language_11()

{

types_11();

references_11();

init_11();

auto r = trailing_return_type(1);

(void) r;

dynamic_memory_11();

func_11();

}

/// @} lang11

/**

@defgroup lambda11 Lambda

https://en.cppreference.com/w/cpp/language/lambda

https://www.geeksforgeeks.org/lambda-expression-in-c/

static void lambda_basics(void)

{

auto annotated_named_lambda_expression = // optional name

[] // capture clause

() // optional list of arguments

{}; // body

// Primitive named lambdas are just like closure functions:

// https://en.wikipedia.org/wiki/Closure_(computer_programming)

// declaration like a function:

// void closure() { };

auto closure = [] {};

closure();

// with arguments

auto pass = [](int a) { return a; };

assert(pass(5) == 5);

// lambda captures external value

int c = 1;

auto get_i = [=]() { return c; };

assert(get_i() == 1);

// lambda captures external variable by reference

// with omitted arguments and return type

auto inc_get = [&] { return ++c; };

assert(inc_get() == 2);

assert(inc_get() == 3);

// annotated expanded empty inline lambda call:

[] // capture

() // optional list of arguments

-> void // optional return value

{} // body

(); // call with arguments

// annotated expanded sample inline lambda call:

c = // result

[c] // capture

(int a) // an argument

-> int // return value

{ return c + a; } // body

(1); // call with argument

assert(c == 4);

// inline lambda which is called in place

// https://en.wikipedia.org/wiki/Anonymous_function

// assert((1 + 1) == 2);

assert([](int a) { return a + 1; }(1) == 2);

// Actually calling lambda inline is useless

// and is provided only for demonstration.

}

/// @cond

static int glob;

/// @endcond

static void lambda_capture(void)

{

// read only

int i = 2;

assert([=] { return i; }() == 2);

// read and write access

[&](int a) { i = a; }(3);

assert(i == 3);

// explicit r/o and r/w

int j;

[i, &j]() { j = i; }();

assert(j == i);

// r/o by default

i++;

[=, &j]() { j = i; }();

assert(j == i);

// r/w by default

i++;

[&, i]() { j = i; }();

assert(j == i);

// can access globals anyway

auto inc_global = []() { return ++glob; };

assert(inc_global() == 1);

assert(inc_global() == 2);

}

/// [utility](https://en.cppreference.com/w/cpp/utility)

void utils_11()

{

pair<int, int> bounds = minmax({3, 2, 1});

assert(bounds.first == 1);

assert(bounds.second == 3);

int min, max;

tie(min, max) = bounds;

assert(min == 1);

int n = 1;

auto t = make_tuple(0, "one", 3.14, ref(n), n);

n = 2;

//cerr << func_type(get<2>(t)) << '\n';

assert(is_arithmetic<decltype(1)>::value);

//assert(is_arithmetic<decltype(get<0>(t))>::value);

assert(get<3>(t) == 2);

assert(get<4>(t) == 1);

}

/// [container](https://en.cppreference.com/w/cpp/container)

template <class L>

void test_list_container(L& l)

{

l.push_front(0);

assert(l.front() == 0);

l.emplace_front(1);

assert(l.front() == 1);

l.pop_front();

L l2;

swap(l, l2);

l.swap(l2);

}

void container_11()

{

// [list_initialization](https://en.cppreference.com/w/cpp/language/list_initialization)

vector<int> v = { 1, 2, 3 };

assert(v.data()[2] == 3);

v.shrink_to_fit();

v.emplace(v.cbegin(), 0);

assert(v.front() == 0);

v.emplace_back(4);

assert(v.back() == 4);

array<int, 1> a1, a2;

swap(a1, a2);

/// [forward_list](https://en.cppreference.com/w/cpp/container/forward_list)

forward_list<int> fl;

test_list_container(fl);

fl.insert_after(fl.cbegin(), 3);

assert(*(next(fl.begin())) == 3);

fl.erase_after(fl.cbefore_begin()); // like fl.pop_front();

assert(fl.front() == 3);

fl.pop_front();

list<int> l;

test_list_container(l);

l.emplace_back(0);

l.emplace(l.begin(), 2);

assert(l.front() == 2);

l.sort();

deque<int> d;

test_list_container(d);

d.emplace_back(0);

stack<int> s, s2;

s.emplace(1);

s.swap(s2);

}

/// [algorithm](https://en.cppreference.com/w/cpp/algorithm)

void algo_11()

{

vector<int> v = { 1, 2, 3 };

assert(find(begin(v), end(v), 0) == end(v));

assert(find(begin(v), end(v), 1) != end(v));

// https://en.cppreference.com/w/cpp/container/vector/erase

// https://en.cppreference.com/w/cpp/algorithm/remove

v.erase(remove_if(v.begin(), v.end(), [](unsigned char x) { return x == 2; }), v.end());

assert(v.size() == 2);

vector<int> r(v.size());

reverse_copy(begin(v), end(v), r.begin());

assert(r[0] > r[1]);

// https://en.cppreference.com/w/cpp/string/basic_string/erase

string s = "1 2 3";

s.erase(remove_if(s.begin(), s.end(), [](unsigned char x) { return isspace(x); }), s.end());

assert(s == "123");

}

/// Compare with @ref sort_03

struct comp {

template <typename T>

bool operator()(const T& l, const T& r) const

{

return l.second < r.second;

}

};

void sort_11()

{

/// [array](https://en.cppreference.com/w/cpp/container/array)

array<int, 10> s { 5, 7, 4, 2, 8, 6, 1, 9, 0, 3 };

sort(s.begin(), s.end(),

// sort using a lambda expression

[](int a, int b) { return a > b; });

// https://stackoverflow.com/questions/18045208/override-mapcompare-with-lambda-function-directly

auto reverse = map<string, int, function<bool(const string&, const string&)>> {

[](const string& a, const string& b) { return a > b; }

}

= {

{ "a", 2 },

{ "b", 1 },

{ "c", 0 },

};

assert(reverse.begin()->first == "c");

assert(reverse.begin()->second == 0);

// https://www.techiedelight.com/sort-map-values-cpp/

typedef pair<string, int> pair;

vector<pair> vec = {

{ "a", 2 },

{ "b", 1 },

{ "c", 0 },

};

sort(vec.begin(), vec.end(),

[](const pair& l, const pair& r) { return l.second < r.second; });

assert(vec.begin()->first == "c");

set<std::pair<string, int>, comp> t = {

{ "a", 2 },

{ "b", 1 },

{ "c", 0 },

};

assert(t.begin()->first == "c");

}

/// @}

/**

@defgroup lambda11_complex More complex Lambdas

/// @cond

/// [function](https://en.cppreference.com/w/cpp/utility/functional/function)

// int use_lambda(int a; int (func*)(int))

static int use_lambda(int a, function<int(int)> f)

{

// lambda argument is like pointer to functions

return f(a);

}

static function<int(int)> g_f;

static void set_lambda(function<int(int)>&& f)

{

g_f = f;

}

static int call_lambda(int a)

{

return g_f(a);

}

/// @endcond

static void lambda_complex(void)

{

auto increment = [](int a) -> int { return a + 1; };

assert(increment(5) == 6);

// named lambda as argument

assert(use_lambda(2, increment) == 3);

set_lambda(increment);

assert(call_lambda(3) == 4);

// inline lambda as argument

assert(use_lambda(1, [](int a) { return a + 1; }) == 2);

int x = 0;

[x]() mutable { assert(++x); }();

assert(x == 0);

}

/// @} lambda11_complex

/**

@defgroup threads11 Threads

[threads](https://en.cppreference.com/w/cpp/thread)

/// @cond

// just function with delay for demonstration

int lento(int a = 0)

{

this_thread::yield();

this_thread::sleep_for(chrono::milliseconds(50));

return a;

}

/// @endcond

/**

[condition_variable](https://en.cppreference.com/w/cpp/thread/condition_variable)

[notify_one](https://en.cppreference.com/w/cpp/thread/condition_variable/notify_one)

void condition_variable_11()

{

mutex m;

int stage = 0;

condition_variable cv;

thread th(

[&m, &stage, &cv] {

unique_lock<mutex> lk(m);

cv.wait(lk, [&stage] { return stage == 1; });

stage = 2;

lk.unlock();

cv.notify_one();

});

// locking block

{

unique_lock<mutex> lk(m);

// https://en.cppreference.com/w/cpp/thread/condition_variable/wait_for

assert(cv.wait_for(lk, chrono::milliseconds(0)) == cv_status::timeout);

assert(!cv.wait_for(lk, chrono::milliseconds(0),[]{return false;}));

}

{

unique_lock<mutex> lk(m);

stage = 1;

}

cv.notify_one();

unique_lock<mutex> lk(m);

cv.wait(lk, [&stage] { return stage == 2; });

th.join();

}

void threads_11()

{

this_thread::yield();

assert(hash<thread::id>()(this_thread::get_id()));

this_thread::sleep_for(chrono::nanoseconds(1));

promise<int> p;

future<int> f = p.get_future();

int v = 0;

thread t([&p, &v] {

lento();

p.set_value(2);

v = 3;

});

assert(v == 0);

assert(f.get() == 2);

lento();

assert(v == 3);

thread t2;

t2.swap(t);

assert(!t.joinable());

assert(t2.joinable());

t2.join();

try {

t2.join();

t2.detach();

} catch (const system_error& e) {

assert(e.code().value() == 22);

}

assert(!t2.joinable());

// detach demo

{

thread t3([&p, &v] {

v = 4;

});

t3.detach();

std::thread { []() { assert(1); } }.detach();

}

lento();

assert(v == 4);

condition_variable_11();

}

void mutex_11()

{

int unguarded = 0, guarded = 0;

mutex m;

thread t1([&unguarded, &guarded, &m] {

unguarded = lento(unguarded) + 1;

lock_guard<mutex> guard(m);

guarded = lento(guarded) + 1;

});

thread t2([&unguarded, &guarded, &m] {

unguarded = lento(unguarded) + 1;

lock_guard<mutex> guard(m);

guarded = lento(guarded) + 1;

});

assert(unguarded == 0);

assert(guarded == 0);

t1.join();

t2.join();

assert(unguarded == 1);

assert(guarded == 2);

}

/// @} threads11

/**

TODO:

function<int(void)> get_a = a;

https://en.cppreference.com/w/cpp/language/attributes

https://en.cppreference.com/w/cpp/language/string_literal

https://en.cppreference.com/w/cpp/language/character_literal

https://en.cppreference.com/w/cpp/language/user_literal

https://en.cppreference.com/w/cpp/language/initializer_list

https://en.cppreference.com/w/cpp/utility/declval

https://en.cppreference.com/w/cpp/language/range-for

https://en.cppreference.com/w/cpp/types/is_move_constructible

https://en.cppreference.com/w/cpp/types/is_constructible

void sig(int)

{

abort();

}

int main(void)

{

signal(SIGALRM, sig);

alarm(1);

language_11();

lambda_basics();

lambda_capture();

lambda_complex();

utils_11();

container_11();

algo_11();

sort_11();

static_assert(constexpr_factorial(4), "");

threads_11();

mutex_11();

return 0;

}

/// @}

examples/cpp/11.cpp at 30ee3e67dcae1f15a46c50a8e2fba1d25a1a7788 · makelinux/examples · GitHub

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