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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 [1]_) 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 [2]_) 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 [3]_, the code is already broken, it | |
| just wasn't generating exceptions. This proposal corrects that | |
| oversight in the language. | |
| References | |
| ========== | |
| .. [1] PEP 239, Adding a Rational Type to Python | |
| http://www.python.org/dev/peps/pep-0239/ | |
| .. [2] PEP 240, Adding a Rational Literal to Python | |
| http://www.python.org/dev/peps/pep-0240/ | |
| .. [3] PEP 8, Style Guide for Python Code | |
| http://www.python.org/dev/peps/pep-0008/ | |
| Copyright | |
| ========= | |
| This document has been placed in the public domain. | |
| .. | |
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