40 lines
1.5 KiB
Factor
40 lines
1.5 KiB
Factor
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USING: help.syntax help.markup kernel prettyprint sequences
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quotations math ;
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IN: sequences.lib
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HELP: map-withn
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{ $values { "seq" sequence } { "quot" quotation } { "n" number } { "newseq" sequence } }
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{ $description "A generalisation of " { $link map } ". The first " { $snippet "n" } " items after the quotation will be "
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"passed to the quotation given to map-withn for each element in the sequence."
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}
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{ $examples
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{ $example "USE: combinators.lib" "1 2 3 4 { 6 7 8 9 10 } [ + + + + ] 4 map-withn .s" "{ 16 17 18 19 20 }" }
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}
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{ $see-also each-withn } ;
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HELP: each-withn
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{ $values { "seq" sequence } { "quot" quotation } { "n" number } }
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{ $description "A generalisation of " { $link each } ". The first " { $snippet "n" } " items after the quotation will be "
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"passed to the quotation given to each-withn for each element in the sequence."
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}
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{ $see-also map-withn } ;
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HELP: sigma
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{ $values { "seq" sequence } { "quot" quotation } { "n" number } }
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{ $description "Like map sum, but without creating an intermediate sequence." }
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{ $example
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"! Find the sum of the squares [0,99]"
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"USING: math.ranges combinators.lib ;"
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"100 [1,b] [ sq ] sigma ."
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"338350"
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} ;
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HELP: count
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{ $values { "seq" sequence } { "quot" quotation } { "n" integer } }
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{ $description "Efficiently returns the number of elements that the predicate quotation matches." }
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{ $example
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"USING: math.ranges combinators.lib ;"
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"100 [1,b] [ even? ] count ."
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"50"
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} ;
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