44 lines
2.6 KiB
Factor
44 lines
2.6 KiB
Factor
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IN: binary-search
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USING: help.markup help.syntax sequences kernel math.order ;
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ARTICLE: "binary-search" "Binary search"
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"The " { $emphasis "binary search" } " algorithm allows elements to be located in sorted sequence in " { $snippet "O(log n)" } " time."
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{ $subsection search }
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"Variants of sequence words optimized for sorted sequences:"
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{ $subsection sorted-index }
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{ $subsection sorted-member? }
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{ $subsection sorted-memq? }
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{ $see-also "order-specifiers" "sequences-sorting" } ;
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ABOUT: "binary-search"
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HELP: search
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{ $values { "seq" "a sorted sequence" } { "quot" "a quotation with stack effect " { $snippet "( elt -- <=> )" } } { "i" "an index, or " { $link f } } { "elt" "an element, or " { $link f } } }
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{ $description "Performs a binary search on a sequence, calling the quotation to decide whether to end the search (" { $link +eq+ } "), search lower (" { $link +lt+ } ") or search higher (" { $link +gt+ } ")."
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$nl
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"If the sequence is non-empty, outputs the index and value of the closest match, which is either an element for which the quotation output " { $link +eq+ } ", or failing that, least element for which the quotation output " { $link +lt+ } "."
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$nl
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"If the sequence is empty, outputs " { $link f } " " { $link f } "." }
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{ $notes "If the sequence has at least one element, this word always outputs a valid index, because it finds the closest match, not necessarily an exact one. In this respect its behavior differs from " { $link find } "." } ;
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{ find find-from find-last find-last find-last-from search } related-words
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HELP: sorted-index
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{ $values { "elt" object } { "seq" "a sorted sequence" } { "i" "an index, or " { $link f } } { "elt" "an element, or " { $link f } } }
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{ $description "Outputs the index and value of the element closest to " { $snippet "elt" } " in the sequence. See " { $link search } " for details." }
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{ $notes "If the sequence has at least one element, this word always outputs a valid index, because it finds the closest match, not necessarily an exact one. In this respect its behavior differs from " { $link index } "." } ;
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{ index index-from last-index last-index-from sorted-index } related-words
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HELP: sorted-member?
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{ $values { "elt" object } { "seq" "a sorted sequence" } { "?" "a boolean" } }
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{ $description "Tests if the sorted sequence contains " { $snippet "elt" } ". Equality is tested with " { $link = } "." } ;
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{ member? sorted-member? } related-words
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HELP: sorted-memq?
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{ $values { "elt" object } { "seq" "a sorted sequence" } { "?" "a boolean" } }
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{ $description "Tests if the sorted sequence contains " { $snippet "elt" } ". Equality is tested with " { $link eq? } "." } ;
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{ memq? sorted-memq? } related-words
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