35 lines
1.1 KiB
Factor
35 lines
1.1 KiB
Factor
USING: help.markup help.syntax kernel words ;
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IN: classes.singleton
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ARTICLE: "singletons" "Singleton classes"
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"A singleton is a class with only one instance and with no state."
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{ $subsection POSTPONE: SINGLETON: }
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{ $subsection define-singleton-class }
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"The set of all singleton classes is itself a class:"
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{ $subsection singleton-class? }
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{ $subsection singleton-class } ;
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HELP: SINGLETON:
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{ $syntax "SINGLETON: class" }
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{ $values
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{ "class" "a new singleton to define" }
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}
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{ $description
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"Defines a new singleton class. The class word itself is the sole instance of the singleton class."
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}
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{ $examples
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{ $example "USING: classes.singleton kernel io ;" "IN: scratchpad" "SINGLETON: foo\nGENERIC: bar ( obj -- )\nM: foo bar drop \"a foo!\" print ;\nfoo bar" "a foo!" }
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} ;
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HELP: define-singleton-class
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{ $values { "word" "a new word" } }
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{ $description
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"Defines a singleton class. This is the run-time equivalent of " { $link POSTPONE: SINGLETON: } "." } ;
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{ POSTPONE: SINGLETON: define-singleton-class } related-words
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HELP: singleton-class
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{ $class-description "The class of singleton classes." } ;
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ABOUT: "singletons"
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