class Natcmp

natcmp.rb

Natural order comparison of two strings e.g. “my_prog_v1.1.0” < “my_prog_v1.2.0” < “my_prog_v1.10.0” which does not follow alphabetically

Based on Martin Pool’s “Natural Order String Comparison” originally written in C sourcefrog.net/projects/natsort/

This software is provided ‘as-is’, without any express or implied warranty. In no event will the authors be held liable for any damages arising from the use of this software.

Permission is granted to anyone to use this software for any purpose, including commercial applications, and to alter it and redistribute it freely, subject to the following restrictions:

The origin of this software must not be misrepresented; you must not claim that you wrote the original software. If you use this software in a product, an acknowledgment in the product documentation would be appreciated but is not required.
Altered source versions must be plainly marked as such, and must not be misrepresented as being the original software.
This notice may not be removed or altered from any source distribution.

Public Class Methods

natcmp (str1, str2, caseInsensitive=false)

Source

# File lib/natcmp.rb, line 32
def self.natcmp(str1, str2, caseInsensitive=false)
  str1, str2 = str1.dup, str2.dup
  compareExpression = /^(\D*)(\d*)(.*)$/

  if caseInsensitive
    str1.downcase!
    str2.downcase!
  end

  # Remove all whitespace
  str1.gsub!(/\s*/, '')
  str2.gsub!(/\s*/, '')

  while (str1.length > 0) or (str2.length > 0) do
    # Extract non-digits, digits and rest of string
    str1 =~ compareExpression
    chars1, num1, str1 = $1.dup, $2.dup, $3.dup

    str2 =~ compareExpression
    chars2, num2, str2 = $1.dup, $2.dup, $3.dup

    # Compare the non-digits
    case (chars1 <=> chars2)
      when 0 # Non-digits are the same, compare the digits...
        # If either number begins with a zero, then compare alphabetically,
        # otherwise compare numerically
        if (num1[0] != 48) and (num2[0] != 48)
          num1, num2 = num1.to_i, num2.to_i
        end

        case (num1 <=> num2)
          when -1 then return -1
          when  1 then return  1
        end
      when -1 then return -1
      when  1 then return  1
    end # case

  end # while

  # Strings are naturally equal
  return 0
end

‘Natural order’ comparison of two strings