Roman Numerals

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The Roman library provides a full-fledged Numeric subclass for working in Roman Numerals.

In most cases this library is probably overkill. Instead, Ruby Facets provides Roman numeral core extension methods for the Integer and String classes which are likely to do everything that one really needs. However, the RomanNumeral class has one advantage. It can be maniputated like any other Numeric object without having to switch back and forth between representations. Moreover, and probably most importantly, it makes an excellect example of how to create a Numeric subclass in Ruby.


We can create Roman numerals via the usual instantiation.    #=> #<RomanNumeral:0x7f10e378ad48 @i=1>

But to make it easier the Integer class is extended with #to_roman.

1.to_roman             #=> #<RomanNumeral:0x7f10e378ad48 @i=1>

Roman numerals can also be formed from their String represnetation.'I')  #=> #<RomanNumeral:0x7f10e378ad48 @i=1>

'I'.to_roman           #=> #<RomanNumeral:0x7f10e378ad48 @i=1>

Because +RomanNumeral+ is a full-fledged subclass of Numeric, we can work with them like we can an Integer.

 a = 2.to_roman        #=> #<RomanNumeral:0x7f10e378ad48 @i=2>
 b = 3.to_roman        #=> #<RomanNumeral:0x7f10e378ad48 @i=3>
 r = a + b             #=> #<RomanNumeral:0x7f10e378ad48 @i=5>

When we want to see the actual Romanized figure, we simple call #to_s.

 r.to_s                #=> "IV"


Using RubyGems:

gem install roman


Copyright (c) 2007 Rubyworks

Roman is destributed under the terms of the BSD-2-Clause license.

Please see LICENSE.txt file for details.