現代 C++ 教程：現代 C++ 的效能與表現力

現代 C++（C++11/14/17）引入了 零成本抽象 用以彌補底層硬體控制與高階可讀性之間的差距。透過確定性的記憶體管理達成效率，而表現力則藉由編譯時期邏輯得以提升。

1. 記憶體配置：std::array 與 std::vector

std::array 是對傳統 C 風格陣列的現代封裝，配置在堆疊上，其大小在編譯時期即已固定。相反地， std::vector 位於堆並動態增長。雖然 std::vector 採用幾何增長倍率（通常為 $1.5\times$ 或 $2\times$），但現代 C++ 提供了 shrink_to_fit() 來回收未使用的容量，提供比像 Go 這類受控語言更精細的控制能力。

2. SFINAE 與類型安全性

透過 std::enable_if 以及 std::is_enum，開發者可以實現 取代失敗非錯誤（SFINAE）。這讓編譯器能在編譯時期根據類型特性選擇特定的函數重載，例如利用其 std::underlying_type來為列舉型別建立通用的輸出運算子。

// C++11 記憶體管理重點
v.push_back(std::move(obj)); // 移動語意
arr.at(0); // 範圍檢查

TERMINALbash — 80x24

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QUESTION 1

Which container is allocated on the stack and has a fixed size defined at compile-time?

std::vector

std::array

std::list

std::deque

QUESTION 2

What is the primary purpose of the shrink_to_fit() member function?

To delete all elements in the container.

To request a reduction in capacity to match the current size.

To sort the elements and remove duplicates.

To move the container to the stack.

QUESTION 3

In the SFINAE example, what does std::underlying_type provide?

The memory address of the enum.

The integral type used to represent the enum.

A string representation of the enum name.

The number of elements in the enum.

QUESTION 4

How does C++ std::vector growth typically differ from Golang slice growth in high-load scenarios?

C++ vectors never grow; they must be pre-allocated.

Golang uses a fixed growth of 10 elements, while C++ is random.

C++ provides explicit control (shrink_to_fit) to manage memory-tight environments.

Golang slices are stored on the stack by default.

QUESTION 5

Which C++11 feature allows a vector to take ownership of a temporary object without copying?

std::enable_if

push_back(T&&) with Rvalue-overload

std::array static size

The 'mutable' keyword