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Ruby/Bsearch: a binary search library for Ruby

Last Modified: 2001-12-23 (Since: 2001-05-05)


Ruby/Bsearch is a binary search library for Ruby. It can search the FIRST or LAST occurrence in an array with a condition given by a block.

The latest version of Ruby/Bsearch is available at <URL:/ruby-bsearch/> .

Example

% irb -r ./bsearch.rb
>> %w(a b c c c d e f).bsearch_first {|x| x <=> "c"}
=> 2
>> %w(a b c c c d e f).bsearch_last {|x| x <=> "c"}
=> 4
>> %w(a b c c c d e f).bsearch_upper_boundary {|x| x <=> "c"}
=> 5
>> %w(a b c e f).bsearch_first {|x| x <=> "c"}
=> 2
>> %w(a b e f).bsearch_first {|x| x <=> "c"}
=> nil
>> %w(a b e f).bsearch_last {|x| x <=> "c"}
=> nil
>> %w(a b e f).bsearch_lower_boundary {|x| x <=> "c"}
=> 2
>> %w(a b e f).bsearch_upper_boundary {|x| x <=> "c"}
=> 2
>> %w(a b c c c d e f).bsearch_range {|x| x <=> "c"}
=> 2...5
>> %w(a b c d e f).bsearch_range {|x| x <=> "c"}
=> 2...3
>> %w(a b d e f).bsearch_range {|x| x <=> "c"}
=> 2...2

Illustration

bsearch illustration
bsearch illustration

API

Array#bsearch_first (range = 0 ... self.length) {|x| ...}
Return the index of the FIRST occurrence in an array with a condition given by block. Return nil if not found. Optional parameter range specifies the range of searching. To search an ascending order array, let the block be like {|x| x <=> key} To search an descending order array, let the block be like {|x| key <=> x}. Naturally, the array should be sorted in advance of searching.
Array#bsearch_last (range = 0 ... self.length) {|x| ...}
Return the index of the LAST occurrence in an array with a condition given by block. Return nil if not fount. Optional parameter range specifies the range of searching. To search an ascending order array, let the block be like {|x| x <=> key} To search an descending order array, let the block be like {|x| key <=> x}. Naturally, the array should be sorted in advance of searching.
Array#bsearch_lower_boundary (range = 0 ... self.length) {|x| ...}
Return the LOWER boundary in an array with a condition given by block. Optional parameter range specifies the range of searching. To search an ascending order array, let the block be like {|x| x <=> key} To search an descending order array, let the block be like {|x| key <=> x}. Naturally, the array should be sorted in advance of searching.
Array#bsearch_upper_boundary (range = 0 ... self.length) {|x| ...}
Return the UPPER boundary in an array with a condition given by block. Optional parameter range specifies the range of searching. To search an ascending order array, let the block be like {|x| x <=> key} To search an descending order array, let the block be like {|x| key <=> x}. Naturally, the array should be sorted in advance of searching.
Array#bsearch_range (range = 0 ... self.length) {|x| ...}
Return both the LOWER and the UPPER boundaries in an array with a condition given by block as Range object. Optional parameter range specifies the range of searching. To search an ascending order array, let the block be like {|x| x <=> key} To search an descending order array, let the block be like {|x| key <=> x}. Naturally, the array should be sorted in advance of searching.
Array#bsearch (range = 0 ... self.length) {|x| ...}
This is an alias to Array#bsearch_first.

Download

Ruby/Bsearch is a free software with ABSOLUTELY NO WARRANTY under the terms of Ruby's license.


Satoru Takabayashi