1 USING: help.markup help.syntax kernel words ;
4 ARTICLE: "singletons" "Singleton classes"
5 "A singleton is a class with only one instance and with no state."
6 { $subsection POSTPONE: SINGLETON: }
7 { $subsection POSTPONE: SINGLETONS: }
8 { $subsection define-singleton-class }
9 "The set of all singleton classes is itself a class:"
10 { $subsection singleton-class? }
11 { $subsection singleton-class } ;
14 { $syntax "SINGLETON: class" }
16 { "class" "a new singleton to define" }
19 "Defines a new singleton class. The class word itself is the sole instance of the singleton class."
22 { $example "USING: classes.singleton kernel io ;" "IN: scratchpad" "SINGLETON: foo\nGENERIC: bar ( obj -- )\nM: foo bar drop \"a foo!\" print ;\nfoo bar" "a foo!" }
25 HELP: define-singleton-class
26 { $values { "word" "a new word" } }
28 "Defines a singleton class. This is the run-time equivalent of " { $link POSTPONE: SINGLETON: } "." } ;
30 { POSTPONE: SINGLETON: define-singleton-class } related-words
33 { $class-description "The class of singleton classes." } ;