Whitespace consists of spaces and newline characters and in some implementations also consists of other characters, such as tabs or form feeds. A token may be surrounded by any number of whitespace characters and comments. Identifiers, numbers, characters, and dot are delimited by whitespace, the start of a comment, an open or close parenthesis, or a string quote. Spacing between items within a production appears for readability only and should be treated as if it were not present. A program consists of a sequence of definitions and expressions.
Derived definitions are syntactic extensions that expand into some form of definition.
A transformer expression is a syntax-rules form or some other expression that produces a transformer. Identifiers may denote variables, keywords, or symbols, depending upon context. They are formed from sequences of letters, digits, and special characters. With three exceptions, identifiers cannot begin with a character that can also begin a number, i.e., they cannot begin with . Data include booleans, numbers, characters, strings, symbols, lists, and vectors.