Identifiers may refer to
Identifiers may be defined as infix operators, by infix and infixr definitions. This affects only the way in which they are parsed and printed: if an identifier @ is declared as an infix operator, constructs of the form @( a, b) are written a @ b. To refer to @ on its own, use ( @). A special case: in any subsequent declaration of @ as a data constructor, @( type_ 1 # type_ 2) is written type_ 1 @ type_ 2.
A number of identifiers are predefined in the module Standard.