Template:cpp/language/condition

Condition

A condition can either be an expression or a simple declaration.

If it can be syntactically resolved as a structured binding declaration, it is interpreted as a structured binding declaration.

(since C++26)

• If it can be syntactically resolved as an expression, it is treated as an expression. Otherwise, it is treated as a declaration that is not a structured binding declaration(since C++26).

When control reaches condition, the condition will yield a value, which is used to .

Expression

If condition is an expression, the value it yields is the the value of the expression.

Declaration

If condition is a simple declaration, the value it yields is the value of the decision variable (see below).

Non-structured binding declaration

The declaration has the following restrictions:

• Syntactically conforms to the following form:

type-specifier-seq declarator = assignment-expression	(until C++11)
attribute-specifier-seq(optional) decl-specifier-seq declarator brace-or-equal-initializer	(since C++11)

• The declarator cannot specify a function or an array.
• The type specifier sequence(until C++11)declaration specifier sequence can only contain type specifiers and constexpr, and it(since C++11) cannot define a class or enumeration.

The decision varaiable of the declaration is the declared variable.

Structured binding declaration The declaration has the following restrictions: The expression in its initializer cannot be of an array type. The declaration specifier sequence can only contain type specifiers and constexpr. The decision variable of the declaration is the invented variable e introduced by the declaration.

(since C++26)