module Abbrev

Calculates the set of unambiguous abbreviations for a given set of strings.

require 'abbrev'
require 'pp'

pp Abbrev.abbrev(['ruby'])
#=>  {"ruby"=>"ruby", "rub"=>"ruby", "ru"=>"ruby", "r"=>"ruby"}

pp Abbrev.abbrev(%w{ ruby rules })

Generates:

{ "ruby"  =>  "ruby",
  "rub"   =>  "ruby",
  "rules" =>  "rules",
  "rule"  =>  "rules",
  "rul"   =>  "rules" }

It also provides an array core extension, Array#abbrev.

pp %w{ summer winter }.abbrev

Generates:

{ "summer"  => "summer",
  "summe"   => "summer",
  "summ"    => "summer",
  "sum"     => "summer",
  "su"      => "summer",
  "s"       => "summer",
  "winter"  => "winter",
  "winte"   => "winter",
  "wint"    => "winter",
  "win"     => "winter",
  "wi"      => "winter",
  "w"       => "winter" }

Public Class Methods

abbrev(words, pattern = nil) click to toggle source

Given a set of strings, calculate the set of unambiguous abbreviations for those strings, and return a hash where the keys are all the possible abbreviations and the values are the full strings.

Thus, given words is “car” and “cone”, the keys pointing to “car” would be “ca” and “car”, while those pointing to “cone” would be “co”, “con”, and “cone”.

require 'abbrev'

Abbrev.abbrev(%w{ car cone })
#=> {"ca"=>"car", "con"=>"cone", "co"=>"cone", "car"=>"car", "cone"=>"cone"}

The optional pattern parameter is a pattern or a string. Only input strings that match the pattern or start with the string are included in the output hash.

Abbrev.abbrev(%w{car box cone crab}, /b/)
#=> {"box"=>"box", "bo"=>"box", "b"=>"box", "crab" => "crab"}

Abbrev.abbrev(%w{car box cone}, 'ca')
#=> {"car"=>"car", "ca"=>"car"}

# File lib/abbrev.rb, line 73
def abbrev(words, pattern = nil)
  table = {}
  seen = Hash.new(0)

  if pattern.is_a?(String)
    pattern = /\A#{Regexp.quote(pattern)}/  # regard as a prefix
  end

  words.each do |word|
    next if word.empty?
    word.size.downto(1) { |len|
      abbrev = word[0...len]

      next if pattern && pattern !~ abbrev

      case seen[abbrev] += 1
      when 1
        table[abbrev] = word
      when 2
        table.delete(abbrev)
      else
        break
      end
    }
  end

  words.each do |word|
    next if pattern && pattern !~ word

    table[word] = word
  end

  table
end

Private Instance Methods

abbrev(words, pattern = nil) click to toggle source

Given a set of strings, calculate the set of unambiguous abbreviations for those strings, and return a hash where the keys are all the possible abbreviations and the values are the full strings.

Thus, given words is “car” and “cone”, the keys pointing to “car” would be “ca” and “car”, while those pointing to “cone” would be “co”, “con”, and “cone”.

require 'abbrev'

Abbrev.abbrev(%w{ car cone })
#=> {"ca"=>"car", "con"=>"cone", "co"=>"cone", "car"=>"car", "cone"=>"cone"}

The optional pattern parameter is a pattern or a string. Only input strings that match the pattern or start with the string are included in the output hash.

Abbrev.abbrev(%w{car box cone crab}, /b/)
#=> {"box"=>"box", "bo"=>"box", "b"=>"box", "crab" => "crab"}

Abbrev.abbrev(%w{car box cone}, 'ca')
#=> {"car"=>"car", "ca"=>"car"}

# File lib/abbrev.rb, line 73
def abbrev(words, pattern = nil)
  table = {}
  seen = Hash.new(0)

  if pattern.is_a?(String)
    pattern = /\A#{Regexp.quote(pattern)}/  # regard as a prefix
  end

  words.each do |word|
    next if word.empty?
    word.size.downto(1) { |len|
      abbrev = word[0...len]

      next if pattern && pattern !~ abbrev

      case seen[abbrev] += 1
      when 1
        table[abbrev] = word
      when 2
        table.delete(abbrev)
      else
        break
      end
    }
  end

  words.each do |word|
    next if pattern && pattern !~ word

    table[word] = word
  end

  table
end