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	PEP: 313
	Title: Adding Roman Numeral Literals to Python
	Version: $Revision$
	Last-Modified: $Date$
	Author: Mike Meyer <mwm@mired.org>
	Status: Rejected
	Type: Standards Track
	Content-Type: text/x-rst
	Created: 01-Apr-2003
	Python-Version: 2.4
	Post-History:


	Abstract
	========

	This PEP (also known as PEP CCCXIII) proposes adding Roman
	numerals as a literal type. It also proposes the new built-in
	function "roman", which converts an object to an integer, then
	converts the integer to a string that is the Roman numeral literal
	equivalent to the integer.


	BDFL Pronouncement
	==================

	This PEP is rejected. While the majority of Python users deemed this
	to be a nice-to-have feature, the community was unable to reach a
	consensus on whether nine should be represented as IX, the modern
	form, or VIIII, the classic form. Likewise, no agreement was
	reached on whether MXM or MCMXC would be considered a well-formed
	representation of 1990. A vocal minority of users has also requested
	support for lower-cased numerals for use in (i) powerpoint slides,
	(ii) academic work, and (iii) Perl documentation.


	Rationale
	=========

	Roman numerals are used in a number of areas, and adding them to
	Python as literals would make computations in those areas easier.
	For instance, Super Bowls are counted with Roman numerals, and many
	older movies have copyright dates in Roman numerals. Further,
	LISP provides a Roman numerals literal package, so adding Roman
	numerals to Python will help ease the LISP-envy sometimes seen in
	comp.lang.python. Besides, the author thinks this is the easiest
	way to get his name on a PEP.


	Syntax for Roman literals
	=========================

	Roman numeral literals will consist of the characters M, D, C, L,
	X, V and I, and only those characters. They must be in upper
	case, and represent an integer with the following rules:

	1. Except as noted below, they must appear in the order M, D, C,
	L, X, V then I. Each occurrence of each character adds 1000, 500,
	100, 50, 10, 5 and 1 to the value of the literal, respectively.

	2. Only one D, V or L may appear in any given literal.

	3. At most three each of Is, Xs and Cs may appear consecutively
	in any given literal.

	4. A single I may appear immediately to the left of the single V,
	followed by no Is, and adds 4 to the value of the literal.

	5. A single I may likewise appear before the last X, followed by
	no Is or Vs, and adds 9 to the value.

	6. X is to L and C as I is to V and X, except the values are 40
	and 90, respectively.

	7. C is to D and M as I is to V and X, except the values are 400
	and 900, respectively.

	Any literal composed entirely of M, D, C, L, X, V and I characters
	that does not follow this format will raise a syntax error,
	because explicit is better than implicit.


	Built-In "roman" Function
	=========================

	The new built-in function "roman" will aide the translation from
	integers to Roman numeral literals. It will accept a single
	object as an argument, and return a string containing the literal
	of the same value. If the argument is not an integer or a
	rational (see :pep:`239`) it will passed through the existing
	built-in "int" to obtain the value. This may cause a loss of
	information if the object was a float. If the object is a
	rational, then the result will be formatted as a rational literal
	(see :pep:`240`) with the integers in the string being Roman
	numeral literals.


	Compatibility Issues
	====================

	No new keywords are introduced by this proposal. Programs that
	use variable names that are all upper case and contain only the
	characters M, D, C, L, X, V and I will be affected by the new
	literals. These programs will now have syntax errors when those
	variables are assigned, and either syntax errors or subtle bugs
	when those variables are referenced in expressions. Since such
	variable names violate :pep:`8`, the code is already broken, it
	just wasn't generating exceptions. This proposal corrects that
	oversight in the language.


	Copyright
	=========

	This document has been placed in the public domain.


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