1require 'rubygems'
2
3##
4# A collection of text-wrangling methods
5
6module Gem::Text
7
8  ##
9  # Wraps +text+ to +wrap+ characters and optionally indents by +indent+
10  # characters
11
12  def format_text(text, wrap, indent=0)
13    result = []
14    work = text.dup
15
16    while work.length > wrap do
17      if work =~ /^(.{0,#{wrap}})[ \n]/ then
18        result << $1.rstrip
19        work.slice!(0, $&.length)
20      else
21        result << work.slice!(0, wrap)
22      end
23    end
24
25    result << work if work.length.nonzero?
26    result.join("\n").gsub(/^/, " " * indent)
27  end
28
29  # This code is based directly on the Text gem implementation
30  # Returns a value representing the "cost" of transforming str1 into str2
31  def levenshtein_distance str1, str2
32    s = str1
33    t = str2
34    n = s.length
35    m = t.length
36    max = n/2
37
38    return m if (0 == n)
39    return n if (0 == m)
40    return n if (n - m).abs > max
41
42    d = (0..m).to_a
43    x = nil
44
45    n.times do |i|
46      e = i+1
47
48      m.times do |j|
49        cost = (s[i] == t[j]) ? 0 : 1
50        x = [
51             d[j+1] + 1, # insertion
52             e + 1,      # deletion
53             d[j] + cost # substitution
54            ].min
55        d[j] = e
56        e = x
57      end
58
59      d[m] = x
60    end
61
62    return x
63  end
64end
65
66