Unary operators act on only one operand in an expression. The unary operators are as follows:

• Indirection operator (*)

• Address-of operator (&)

• Unary plus operator (+)

• Unary negation operator (-)

• Logical negation operator (!)

• One's complement operator (~)

• Prefix increment operator (++)

• Prefix decrement operator (--)

• Cast operator ()

• sizeof operator

• alignof operator

• noexcept expression

• new operator

• delete operator

These operators have right-to-left associativity. Unary expressions generally involve syntax that precedes a postfix or primary expression.

unary-expression:
  postfix-expression
  ++ cast-expression
  -- cast-expression
  unary-operator cast-expression
  sizeof unary-expression
  sizeof ( type-id )
  sizeof ... ( identifier )
  alignof ( type-id )
  noexcept-expression
  new-expression
  delete-expression
unary-operator: one of
  * & + - ! ~

Any postfix-expression is considered a unary-expression, and because any primary-expression is considered a postfix-expression, any primary-expression is considered a unary-expression also. For more information, see Postfix expressions and Primary expressions.

The cast-expression is a unary-expression with an optional cast to change the type. For more information, see Cast operator: ().

The noexcept-expression is a noexcept-specifier with a constant-expression argument. For more information, see noexcept.

The new-expression refers to the new operator. The delete-expression refers to the delete operator. For more information, see new operator and delete operator.

Types of expressions