Warning: This is the manual of the legacy Guile 2.0 series. You may want to read the manual of the current stable series instead.

7.6.2.24 rnrs enums

The (rnrs enums (6)) library provides structures and procedures for working with enumerable sets of symbols. Guile’s implementation defines an enum-set record type that encapsulates a finite set of distinct symbols, the universe, and a subset of these symbols, which define the enumeration set.

The SRFI-1 list library provides a number of procedures for performing set operations on lists; Guile’s (rnrs enums) implementation makes use of several of them. See SRFI-1 Set Operations, for more information.

Scheme Procedure: make-enumeration symbol-list

Returns a new enum-set whose universe and enumeration set are both equal to symbol-list, a list of symbols.

Scheme Procedure: enum-set-universe enum-set

Returns an enum-set representing the universe of enum-set, an enum-set.

Scheme Procedure: enum-set-indexer enum-set

Returns a procedure that takes a single argument and returns the zero-indexed position of that argument in the universe of enum-set, or #f if its argument is not a member of that universe.

Scheme Procedure: enum-set-constructor enum-set

Returns a procedure that takes a single argument, a list of symbols from the universe of enum-set, an enum-set, and returns a new enum-set with the same universe that represents a subset containing the specified symbols.

Scheme Procedure: enum-set->list enum-set

Returns a list containing the symbols of the set represented by enum-set, an enum-set, in the order that they appear in the universe of enum-set.

Scheme Procedure: enum-set-member? symbol enum-set

Scheme Procedure: enum-set-subset? enum-set1 enum-set2

Scheme Procedure: enum-set=? enum-set1 enum-set2

These procedures test for membership of symbols and enum-sets in other enum-sets. enum-set-member? returns #t if and only if symbol is a member of the subset specified by enum-set. enum-set-subset? returns #t if and only if the universe of enum-set1 is a subset of the universe of enum-set2 and every symbol in enum-set1 is present in enum-set2. enum-set=? returns #t if and only if enum-set1 is a subset, as per enum-set-subset? of enum-set2 and vice versa.

Scheme Procedure: enum-set-union enum-set1 enum-set2

Scheme Procedure: enum-set-intersection enum-set1 enum-set2

Scheme Procedure: enum-set-difference enum-set1 enum-set2

These procedures return, respectively, the union, intersection, and difference of their enum-set arguments.

Scheme Procedure: enum-set-complement enum-set

Returns enum-set’s complement (an enum-set), with regard to its universe.

Scheme Procedure: enum-set-projection enum-set1 enum-set2

Returns the projection of the enum-set enum-set1 onto the universe of the enum-set enum-set2.

Scheme Syntax: define-enumeration type-name (symbol ...) constructor-syntax

Evaluates to two new definitions: A constructor bound to constructor-syntax that behaves similarly to constructors created by enum-set-constructor, above, and creates new enum-sets in the universe specified by (symbol ...); and a “predicate macro” bound to type-name, which has the following form:

(type-name sym)

If sym is a member of the universe specified by the symbols above, this form evaluates to sym. Otherwise, a &syntax condition is raised.