59 lines
3.0 KiB
Factor
59 lines
3.0 KiB
Factor
USING: arrays help.markup help.syntax strings sbufs
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vectors kernel combinators ;
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IN: quotations
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ARTICLE: "quotations" "Quotations"
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"Conceptually, a quotation is an anonymous function (a value denoting a snippet of code) which can be passed around and called."
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$nl
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"Concretely, a quotation is an immutable sequence of objects, some of which may be words, together with a block of machine code which may be executed to achieve the effect of evaluating the quotation. The machine code is generated by a fast non-optimizing quotation compiler which is always running and is transparent to the developer."
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$nl
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"Quotations evaluate sequentially from beginning to end. Literals are pushed on the stack and words are executed. Details can be found in " { $link "evaluator" } "."
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$nl
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"Quotation literal syntax is documented in " { $link "syntax-quots" } "."
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$nl
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"Quotations implement the " { $link "sequence-protocol" } ", and existing sequences can be converted into quotations:"
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{ $subsection >quotation }
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{ $subsection 1quotation }
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"Wrappers are used to push words on the data stack; they evaluate to the object being wrapped:"
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{ $subsection wrapper }
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{ $subsection literalize }
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{ $see-also "dataflow" "combinators" } ;
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ABOUT: "quotations"
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HELP: callable
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{ $class-description "The class whose instances can be passed to " { $link call } ". This includes quotations and composed quotations built up with " { $link curry } " or " { $link compose } "." } ;
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HELP: quotation
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{ $description "The class of quotations. See " { $link "syntax-quots" } " for syntax and " { $link "quotations" } " for general information." } ;
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HELP: >quotation
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{ $values { "seq" "a sequence" } { "quot" quotation } }
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{ $description "Outputs a freshly-allocated quotation with the same elements as a given sequence." } ;
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HELP: 1quotation
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{ $values { "obj" object } { "quot" quotation } }
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{ $description "Constructs a quotation holding one element." }
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{ $notes
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"The following two phrases are equivalent:"
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{ $code "\\ reverse execute" }
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{ $code "\\ reverse 1quotation call" }
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} ;
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HELP: wrapper
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{ $description "The class of wrappers. Wrappers are created by calling " { $link literalize } ". See " { $link "syntax-words" } " for syntax." } ;
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HELP: <wrapper> ( obj -- wrapper )
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{ $values { "obj" object } { "wrapper" wrapper } }
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{ $description "Creates an object which pushes " { $snippet "obj" } " on the stack when evaluated. User code should call " { $link literalize } " instead, since it avoids wrapping self-evaluating objects (which is redundant)." } ;
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HELP: literalize
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{ $values { "obj" object } { "wrapped" object } }
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{ $description "Outputs an object which evaluates to " { $snippet "obj" } " when placed in a quotation. If " { $snippet "obj" } " is not self-evaluating (for example, it is a word), then it will be wrapped." }
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{ $examples
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{ $example "USING: prettyprint quotations ;" "5 literalize ." "5" }
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{ $example "USING: math prettyprint quotations sequences ;" "[ + ] [ literalize ] map ." "[ \\ + ]" }
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} ;
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{ literalize curry <wrapper> POSTPONE: \ POSTPONE: W{ } related-words
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