Scheme R5RS defines two types of s-expressions. Standard list beginning with '(' and vector beginning with '#('. The SExprType data type indicates which one was parsed.

The SchemeToken data type defines the atoms of an Scheme R5RS s-expression. An SExpr SExprType SchemeToken object containning the atoms TQuote, TQuasiquote, TComma, TCommaAt and TDot need futher processing in order to get what the R5RS report calls a datum. See also Datum.

The tokenParser parses a SchemeToken

The sexpr defines a SExprParser to parse a Scheme R5RS s-expression as an SExpr SExprType SchemeToken. If you also want source position see the withLocation function.

Space is optional before and after the following tokens:

• TString
• TQuote
• TQuasiquote
• TComma
• TCommaAt

The Datum data type implements the Scheme R5RS definition of a Datum. See also sexpr2Datum.

The sexpr2Datum function takes a list of SchemeToken and returns a list of Datum. In case of failure it will report an error, hence the Either data type in the signature.

As defined in the Scheme R5RS report, the TQuote, TQuasiquote, TComma, TCommaAt and TDot tokens must be followed by another token.

The whitespace parser parses one space, tab or end of line (\n and \r\n).

The comment parser parses a semi-colon (;) character and everything until the end of line included.

The interTokenSpace parser parses zero or more whitespace or comment.

The interTokenSpace1 parser parses one or more whitespace or comment.

The identifier parser parses a Scheme R5RS identifier.

The boolean parser parses a Scheme R5RS boolean (#t or #f).

The character parser parses a Scheme R5RS character.

The stringParser parser parses a Scheme R5RS character.

The quote parser parses a quote character (').

The quasiquote parser parses a quasiquote character (`).

The comma parser parses a comma (,).

The commaAt parser parses a comma followed by @ (,@).

The dot parser parses a single dot character (.).

A Scheme R5RS number is an exact or inexact complex number.

A Scheme R5RS number is either exact or inexact. The paragraph 6.4.2 from the R5RS report should clarify the meaning of exact and inexact :

"""A numerical constant may be specified to be either exact or inexact by a prefix. The prefixes are #e for exact, and #i for inexact. An exactness prefix may appear before or after any radix prefix that is used. If the written representation of a number has no exactness prefix, the constant may be either inexact or exact. It is inexact if it contains a decimal point, an exponent, or a “#” character in the place of a digit, otherwise it is exact."""

The Complex data type represents a Scheme R5RS complex number.

The SReal data type represents a Scheme R5RS real number.

The Sign datatype indicates if a number is positive (Plus) or negative (Minus)

A Scheme R5RS unsigned integer can be written in three ways.

• With digits only
• With digits and # signs
• With only # signs in some special context.

A Scheme R5RS number can have many # signs at the end. This type alias indicates the number of # signs parsed.

Scheme R5RS defines 5 types of machine precision for a decimal number. The machine precision is specified in the suffix (see Suffix).

The Suffix data type represents the suffix for a Scheme R5RS decimal number. It is a based 10 exponent.

The number parser parses a Scheme R5RS number.