Re: Grammar for roman numerals

On 29 Mar 2007 23:05:56 -0400, Ivan Boldyrev wrote:


> On 9791 day of my life msully wrote:
>> One of the exercises I am doing is writing a grammar for roman
>> numerals.
> ...
>> Comments?
>
> Now rewrite the grammar as a regular expression :)


Not in "regulars", but the following more or less obvious pattern


NOEMPTY
( ['M'['M'['M']]]
    ['C'['D'|'M'|'C'['C']] | 'D'['C'['C'['C']]]]
    ['X'['L'|'C'|'X'['X']] | 'L'['X'['X'['X']]]]
    ['I'['V'|'X'|'I'['I']] | 'V'['I'['I'['I']]]]
)


should do the trick. More complex were to use immediate assignments for
evaluation of the numeral's value it gets matched. But it is also doable.
Though a hand-written scanner would be faster and cleaner.


--
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de

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