Merge branch 'master' of github.com:AnthonyCalandra/modern-cpp-features

CPP11.md

@@ -13,7 +13,7 @@ C++11 includes the following new language features:
 - [auto](#auto)
 - [lambda expressions](#lambda-expressions)
 - [decltype](#decltype)
-- [template aliases](#template-aliases)
+- [type aliases](#type-aliases)
 - [nullptr](#nullptr)
 - [strongly-typed enums](#strongly-typed-enums)
 - [attributes](#attributes)
@@ -33,6 +33,7 @@ C++11 includes the following new language features:
 - [right angle brackets](#right-angle-brackets)
 - [ref-qualified member functions](#ref-qualified-member-functions)
 - [trailing return types](#trailing-return-types)
+- [noexcept specifier](#noexcept-specifier)
 
 C++11 includes the following new library features:
 - [std::move](#stdmove)
@@ -49,6 +50,7 @@ C++11 includes the following new library features:
 - [std::make_shared](#stdmake_shared)
 - [memory model](#memory-model)
 - [std::async](#stdasync)
+- [std::begin/end](#stdbeginend)
 
 ## C++11 Language Features
 
@@ -128,6 +130,19 @@ static_assert(arity<>::value == 0);
 static_assert(arity<char, short, int>::value == 3);
 ```
 
+An interesting use for this is creating an _initializer list_ from a _parameter pack_ in order to iterate over variadic function arguments.
+```c++
+template <typename First, typename... Args>
+auto sum(const First first, const Args... args) -> decltype(first) {
+  const auto values = {first, args...};
+  return std::accumulate(values.begin(), values.end(), First{0});
+}
+
+sum(1, 2, 3, 4, 5); // 15
+sum(1, 2, 3);       // 6               
+sum(1.5, 2.0, 3.7); // 7.2
+```
+
 ### Initializer lists
 A lightweight array-like container of elements created using a "braced list" syntax. For example, `{ 1, 2, 3 }` creates a sequences of integers, that has type `std::initializer_list<int>`. Useful as a replacement to passing a vector of objects to a function.
 ```c++
@@ -243,8 +258,8 @@ add(1, 2.0); // `decltype(x + y)` => `decltype(3.0)` => `double`
 
 See also: `decltype(auto)` (C++14).
 
-### Template aliases
+### Type aliases
-Semantically similar to using a `typedef` however, template aliases with `using` are easier to read and are compatible with templates.
+Semantically similar to using a `typedef` however, type aliases with `using` are easier to read and are compatible with templates.
 ```c++
 template <typename T>
 using Vec = std::vector<T>;
@@ -645,6 +660,27 @@ auto add(T a, U b) -> decltype(a + b) {
 ```
 In C++14, `decltype(auto)` can be used instead.
 
+### Noexcept specifier
+The `noexcept` specifier specifies whether a function could throw exceptions. It is an improved version of `throw()`.
+
+```c++
+void func1() noexcept;        // does not throw
+void func2() noexcept(true);  // does not throw
+void func3() throw();         // does not throw
+
+void func4() noexcept(false); // may throw
+```
+
+Non-throwing functions are permitted to call potentially-throwing functions. Whenever an exception is thrown and the search for a handler encounters the outermost block of a non-throwing function, the function std::terminate is called.
+
+```c++
+extern void f();  // potentially-throwing
+void g() noexcept {
+    f();          // valid, even if f throws
+    throw 42;     // valid, effectively a call to std::terminate
+}
+```
+
 ## C++11 Library Features
 
 ### std::move
@@ -861,6 +897,23 @@ auto handle = std::async(std::launch::async, foo);  // create an async task
 auto result = handle.get();  // wait for the result
 ```
 
+### std::begin/end
+`std::begin` and `std::end` free functions were added to return begin and end iterators of a container generically. These functions also work with raw arrays which do not have begin and end member functions.
+
+```c++
+template <typename T>
+int CountTwos(const T& container) {
+  return std::count_if(std::begin(container), std::end(container), [](int item) {
+    return item == 2;
+  });
+}
+
+std::vector<int> vec = {2,2,43,435,4543,534};
+int arr[8] = {2,43,45,435,32,32,32,32};
+auto a = CountTwos(vec); // 2
+auto b = CountTwos(arr);  // 1
+```
+
 ## Acknowledgements
 * [cppreference](http://en.cppreference.com/w/cpp) - especially useful for finding examples and documentation of new library features.
 * [C++ Rvalue References Explained](http://thbecker.net/articles/rvalue_references/section_01.html) - a great introduction I used to understand rvalue references, perfect forwarding, and move semantics.

CPP17.md

@@ -178,6 +178,18 @@ const auto [ x, y ] = origin();
 x; // == 0
 y; // == 0
 ```
+```c++
+std::unordered_map<std::string, int> mapping {
+  {"a", 1},
+  {"b", 2},
+  {"c", 3},
+};
+
+// Destructure by reference.
+for (const auto& [key, value] : mapping) {
+  // Do something with key and value
+}
+```
 
 ### Selection statements with initializer
 New versions of the `if` and `switch` statements which simplify common code patterns and help users keep scopes tight.

README.md

@@ -62,7 +62,7 @@ C++11 includes the following new language features:
 - [auto](#auto)
 - [lambda expressions](#lambda-expressions)
 - [decltype](#decltype)
-- [template aliases](#template-aliases)
+- [type aliases](#type-aliases)
 - [nullptr](#nullptr)
 - [strongly-typed enums](#strongly-typed-enums)
 - [attributes](#attributes)
@@ -82,6 +82,7 @@ C++11 includes the following new language features:
 - [right angle brackets](#right-angle-brackets)
 - [ref-qualified member functions](#ref-qualified-member-functions)
 - [trailing return types](#trailing-return-types)
+- [noexcept specifier](#noexcept-specifier)
 
 C++11 includes the following new library features:
 - [std::move](#stdmove)
@@ -98,6 +99,7 @@ C++11 includes the following new library features:
 - [std::make_shared](#stdmake_shared)
 - [memory model](#memory-model)
 - [std::async](#stdasync)
+- [std::begin/end](#stdbeginend)
 
 ## C++20 Language Features
 
@@ -429,6 +431,18 @@ const auto [ x, y ] = origin();
 x; // == 0
 y; // == 0
 ```
+```c++
+std::unordered_map<std::string, int> mapping {
+  {"a", 1}, 
+  {"b", 2}, 
+  {"c", 3},
+};
+
+// Destructure by reference.
+for (const auto& [key, value] : mapping) {
+  // Do something with key and value
+}
+```
 
 ### Selection statements with initializer
 New versions of the `if` and `switch` statements which simplify common code patterns and help users keep scopes tight.
@@ -939,6 +953,19 @@ static_assert(arity<>::value == 0);
 static_assert(arity<char, short, int>::value == 3);
 ```
 
+An interesting use for this is creating an _initializer list_ from a _parameter pack_ in order to iterate over variadic function arguments.
+```c++
+template <typename First, typename... Args>
+auto sum(const First first, const Args... args) -> decltype(first) {
+  const auto values = {first, args...};
+  return std::accumulate(values.begin(), values.end(), First{0});
+}
+
+sum(1, 2, 3, 4, 5); // 15
+sum(1, 2, 3);       // 6
+sum(1.5, 2.0, 3.7); // 7.2
+```
+
 ### Initializer lists
 A lightweight array-like container of elements created using a "braced list" syntax. For example, `{ 1, 2, 3 }` creates a sequences of integers, that has type `std::initializer_list<int>`. Useful as a replacement to passing a vector of objects to a function.
 ```c++
@@ -1054,8 +1081,8 @@ add(1, 2.0); // `decltype(x + y)` => `decltype(3.0)` => `double`
 
 See also: [`decltype(auto)`](#decltypeauto).
 
-### Template aliases
+### Type aliases
-Semantically similar to using a `typedef` however, template aliases with `using` are easier to read and are compatible with templates.
+Semantically similar to using a `typedef` however, type aliases with `using` are easier to read and are compatible with templates.
 ```c++
 template <typename T>
 using Vec = std::vector<T>;
@@ -1457,6 +1484,27 @@ auto add(T a, U b) -> decltype(a + b) {
 ```
 In C++14, [decltype(auto)](#decltypeauto) can be used instead.
 
+### Noexcept specifier
+The `noexcept` specifier specifies whether a function could throw exceptions. It is an improved version of `throw()`.
+
+```c++
+void func1() noexcept;        // does not throw
+void func2() noexcept(true);  // does not throw
+void func3() throw();         // does not throw
+
+void func4() noexcept(false); // may throw
+```
+
+Non-throwing functions are permitted to call potentially-throwing functions. Whenever an exception is thrown and the search for a handler encounters the outermost block of a non-throwing function, the function std::terminate is called.
+
+```c++
+extern void f();  // potentially-throwing
+void g() noexcept {
+    f();          // valid, even if f throws
+    throw 42;     // valid, effectively a call to std::terminate
+}
+```
+
 ## C++11 Library Features
 
 ### std::move
@@ -1673,6 +1721,23 @@ auto handle = std::async(std::launch::async, foo);  // create an async task
 auto result = handle.get();  // wait for the result
 ```
 
+### std::begin/end
+`std::begin` and `std::end` free functions were added to return begin and end iterators of a container generically. These functions also work with raw arrays which do not have begin and end member functions.
+
+```c++
+template <typename T>
+int CountTwos(const T& container) {
+  return std::count_if(std::begin(container), std::end(container), [](int item) {
+    return item == 2;
+  });
+}
+
+std::vector<int> vec = {2,2,43,435,4543,534};
+int arr[8] = {2,43,45,435,32,32,32,32};
+auto a = CountTwos(vec); // 2
+auto b = CountTwos(arr);  // 1
+```
+
 ## Acknowledgements
 * [cppreference](http://en.cppreference.com/w/cpp) - especially useful for finding examples and documentation of new library features.
 * [C++ Rvalue References Explained](http://thbecker.net/articles/rvalue_references/section_01.html) - a great introduction I used to understand rvalue references, perfect forwarding, and move semantics.