Keywords

Keywords are reserved tokens whose role in the language is defined in the language specification. They may not be used as identifiers.

Usage

Usage depends on the keyword in question.

Description

The following are reserved keywords:

• abstracts (currently unused)
• alias
• assembly (currently unused)
• assert
• assign
• break
• case
• catch
• class
• continue
• dynamic
• else (used with the for, if and switch statements, in the if expression and as an operator)
• exists (used with if and as an operator)
• extends used in class declarations to specify the superclass and invoke superclass initializers, and also in constructor declarations to invoke superclass constructors.
• finally
• for
• function
• given
• if used for the if statement and the if expression
• import
• in (used for variance and with the for statement and as an operator)
• interface
• is (used in the if, while, and case statements and as an operator)
• let
• module
• new
• nonempty (used in the if, while, and case statements and as an operator)
• object
• of (used with class and interface declarations) and as an operator)
• out
• outer
• package
• return
• satisfies (used in class and interface declarations)
• super
• switch is used for the switch statement and the switch expression
• then is used in if expressions and also as the then operator
• this
• throw
• try
• value
• void
• while

Quoting

It is possible to quote keywords, creating an identifier from a character sequence which would otherwise be treated as keyword by the lexer. For example \iout creates an identifier called out. The intended purpose of quoting is interoperation with other languages. For example, it may be necessary to invoke or refine a method named out on a class written in Java (where out is not a keyword).

Annotations

Other identifiers commonly seen in declarations (such as shared) are not keywords but annotations.

See also

• Identifiers and keywords in the Ceylon specification