58 lines
1.3 KiB
Ruby
58 lines
1.3 KiB
Ruby
module DidYouMean
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module Levenshtein # :nodoc:
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# This code is based directly on the Text gem implementation
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# Copyright (c) 2006-2013 Paul Battley, Michael Neumann, Tim Fletcher.
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#
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# Returns a value representing the "cost" of transforming str1 into str2
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def distance(str1, str2)
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n = str1.length
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m = str2.length
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return m if n.zero?
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return n if m.zero?
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d = (0..m).to_a
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x = nil
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# to avoid duplicating an enumerable object, create it outside of the loop
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str2_codepoints = str2.codepoints
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str1.each_codepoint.with_index(1) do |char1, i|
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j = 0
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while j < m
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cost = (char1 == str2_codepoints[j]) ? 0 : 1
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x = min3(
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d[j+1] + 1, # insertion
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i + 1, # deletion
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d[j] + cost # substitution
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)
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d[j] = i
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i = x
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j += 1
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end
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d[m] = x
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end
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x
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end
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module_function :distance
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private
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# detects the minimum value out of three arguments. This method is
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# faster than `[a, b, c].min` and puts less GC pressure.
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# See https://github.com/ruby/did_you_mean/pull/1 for a performance
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# benchmark.
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def min3(a, b, c)
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if a < b && a < c
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a
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elsif b < c
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b
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else
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c
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end
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end
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module_function :min3
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end
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end
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