How Should I Use C 11's Range-Based For Loop for Observing and Modifying Container Elements?

How should C 11's range-based for be used?

Syntax:

The syntax for C 11's range-based for loop varies depending on the desired operation on the container elements:

Observing elements:

• For just observing the elements, capture by const reference: for (const auto& elem : container)

  • For cheap-to-copy types, simplify to: for (auto elem : container) if desired.

Modifying elements:

• Capture by (non-const) reference: for (auto& elem : container)

  • For containers with proxy iterators (like std::vector), use: for (auto&& elem : container)

Guidelines:

Observing vs. Modifying

Observing:

• The goal is to access elements without modifying them.
• Use for (const auto& elem : container) or for (auto elem : container) when elements are cheap to copy.

Modifying:

• The goal is to modify elements in place.
• Use for (auto& elem : container).
• For proxy iterators, use: for (auto&& elem : container).

Generic Code:

In generic code, to ensure compatibility with diverse types and containers:

Observing:

• Always use for (const auto& elem : container).

Modifying:

• Use for (auto&& elem : container).

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