60 lines
3.1 KiB
Factor
60 lines
3.1 KiB
Factor
IN: binary-search
|
|
USING: help.markup help.syntax sequences kernel math.order ;
|
|
|
|
HELP: search
|
|
{ $values { "seq" "a sorted sequence" } { "quot" { $quotation ( elt -- <=> ) } } { "i" "an index, or " { $link f } } { "elt" "an element, or " { $link f } } }
|
|
{ $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+ } ")."
|
|
$nl
|
|
"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+ } "."
|
|
$nl
|
|
"If the sequence is empty, outputs " { $link f } " " { $link f } "." }
|
|
{ $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 } "." }
|
|
{ $examples
|
|
"Searching for an integer in a sorted array:"
|
|
{ $example
|
|
"USING: binary-search math.order prettyprint ;"
|
|
"{ -13 -4 1 9 16 17 28 } [ 5 >=< ] search . ."
|
|
"1\n2"
|
|
}
|
|
"Frequently, the quotation passed to " { $link search } " is constructed by " { $link curry } " or " { $link with } " in order to make the search key a parameter:"
|
|
{ $example
|
|
"USING: binary-search kernel math.order prettyprint ;"
|
|
"5 { -13 -4 1 9 16 17 28 } [ <=> ] with search . ."
|
|
"1\n2"
|
|
}
|
|
} ;
|
|
|
|
{ find find-from find-last find-last find-last-from search } related-words
|
|
|
|
HELP: sorted-index
|
|
{ $values { "obj" object } { "seq" "a sorted sequence" } { "i" "an index, or " { $link f } } }
|
|
{ $description "Outputs the index of the element closest to " { $snippet "elt" } " in the sequence. See " { $link search } " for details." }
|
|
{ $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 } "." } ;
|
|
|
|
{ index index-from last-index last-index-from sorted-index } related-words
|
|
|
|
HELP: sorted-member?
|
|
{ $values { "obj" object } { "seq" "a sorted sequence" } { "?" boolean } }
|
|
{ $description "Tests if the sorted sequence contains " { $snippet "elt" } ". Equality is tested with " { $link = } "." } ;
|
|
|
|
{ member? sorted-member? } related-words
|
|
|
|
HELP: sorted-member-eq?
|
|
{ $values { "obj" object } { "seq" "a sorted sequence" } { "?" boolean } }
|
|
{ $description "Tests if the sorted sequence contains " { $snippet "elt" } ". Equality is tested with " { $link eq? } "." } ;
|
|
|
|
{ member-eq? sorted-member-eq? } related-words
|
|
|
|
ARTICLE: "binary-search" "Binary search"
|
|
"The " { $emphasis "binary search" } " algorithm allows elements to be located in sorted sequence in " { $snippet "O(log n)" } " time."
|
|
{ $subsections search }
|
|
"Variants of sequence words optimized for sorted sequences:"
|
|
{ $subsections
|
|
sorted-index
|
|
sorted-member?
|
|
sorted-member-eq?
|
|
}
|
|
{ $see-also "order-specifiers" "sequences-sorting" } ;
|
|
|
|
ABOUT: "binary-search"
|