In Standard ML, there are syntactically two kinds of identifiers.
-
Alphanumeric: starts with a letter or prime (
') and is followed by letters, digits, primes and underbars (_).Examples:
abc,ABC123,Abc_123,'a. -
Symbolic: a sequence of the following
! % & $ # + - / : < = > ? @ | ~ ` ^ | *
Examples:
+=,<=,>>,$.
With the exception of =, reserved words can not be identifiers.
There are a number of different classes of identifiers, some of which have additional syntactic rules.
-
Identifiers not starting with a prime.
-
value identifier (includes variables and constructors)
-
type constructor
-
structure identifier
-
signature identifier
-
functor identifier
-
-
Identifiers starting with a prime.
-
type variable
-
-
Identifiers not starting with a prime and numeric labels (
1,2, …).-
record label
-