When Should Brace-Enclosed Initialization Syntax Be Used in C 11?

When to Use Brace-Enclosed Initialization in C 11

C 11 introduced brace-enclosed initialization syntax, providing a myriad of options for initializing variables. However, the choice of syntax can significantly impact the semantics of the code, especially in template contexts. To address this, it's crucial to adhere to a consistent guideline to ensure clarity and correctness.

Guiding Principle:

1. Exact Value Initialization:

   • Use copy (=) initialization to assign an explicit value to an object, effectively avoiding potential constructor ambiguities.
   • If copy initialization is not available, consider brace initialization if it maintains the correct semantics. Otherwise, use parenthesis initialization.

2. Storage Value Initialization:

   • Utilize brace initialization to specify a list of values to be stored within the object, such as elements in vectors and complex numbers.

3. Descriptive Value Initialization:

   • Employ parenthesis initialization for values that describe the intended state of an object, i.e., parameters that influence its behavior rather than being directly stored. This includes arguments for vectors (size) and file names for ifstreams.

Example Demonstration:

• Example 1-2: Copy initialization ensures accurate initialization.
• Example 3: Brace initialization is appropriate for storing a specific number of 'x' characters in a string.
• Example 4: Brace initialization is used to initialize a function object (std::function).
• Example 5: Both brace and parenthesis initialization work for std::unique_ptr.
• Example 6-7: Brace initialization provides a more concise syntax for initializing std::locale and std::default_random_engine.
• Example 8: Brace initialization is preferred for initializing duration objects as it is more idiomatic and efficient.

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