Why Use Curly Braces for Object Initialization in C ?

Advantages of Initialization Lists (Curly Braces)

Like the question suggests, initializing objects using curly braces (list initialization) offers several advantages over other methods. In particular, it provides a clearer and less error-prone way to construct objects compared to the following alternatives:

MyClass a1 {a};     // list initialization
MyClass a2 = {a}; // copy initialization
MyClass a3 = a;    // copy initialization using an object
MyClass a4(a);     // constructor initialization

The primary advantage of list initialization is that it prevents narrowing conversions. This means that it does not allow data to be converted from a wider type to a narrower type, which can lead to potential loss of precision or data corruption. Here are the disallowed conversions:

• Integer to integer (with narrow destination)
• Floating-point to floating-point (with narrow destination)
• Floating-point to integer
• Integer to floating-point

For example, the following initialization using curly braces would result in an error, as the value 7.9 cannot fit into a char without truncation:

char c2 { 7.9 }; // error: possible truncation

In contrast, the other initialization methods allow narrowing conversions, potentially leading to unexpected results. Consider the following:

char c2 = 7.9; // sets c2 to 7, truncating the decimal part

Another advantage of list initialization is that it distinguishes between types and values. When using the auto keyword to infer the type from the initializer, curly braces are required to create an object. This is in contrast to the assignment operator (=), which initializes a variable with a specific type. For example:

auto z1 {99};   // z1 is an int
auto z2 = {99}; // z2 is std::initializer_list<int>

In conclusion, list initialization using curly braces is generally preferred over other initialization methods. It provides a clearer and less error-prone way to construct objects by preventing narrowing conversions and distinguishing between types and values.

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