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Revised(5) Scheme

2.1 Identifiers

Most identifiers allowed by other programming languages are also acceptable to Scheme. The precise rules for forming identifiers vary among implementations of Scheme, but in all implementations a sequence of letters, digits, and "extended alphabetic characters" that begins with a character that cannot begin a number is an identifier. In addition, +, -, and ... are identifiers. Here are some examples of identifiers:

lambda q list->vector soup + V17a <=? a34kTMNs the-word-recursion-has-many-meanings

Extended alphabetic characters may be used within identifiers as if they were letters. The following are extended alphabetic characters:

! $ % & * + - . / : < = > ? @ ^ _ ~

See section 7.1.1 Lexical structure for a formal syntax of identifiers.

Identifiers have two uses within Scheme programs:

• Any identifier may be used as a variable or as a syntactic keyword (see sections see section 3.1 Variables; syntactic keywords; and regions and see section 4.3 Macros).

• When an identifier appears as a literal or within a literal (see section see section 4.1.2 Literal expressions), it is being used to denote a symbol (see section see section 6.3.3 Symbols).