Asp Forum - Re: [QUIZ] Roman Numerals (#22

Dave Burt

3/7/2005 2:05:00 PM

Hello mailing list. This has already been posted on Usenet, sorry for the
duplication. (The gateway seems to be one-way at the moment.)

Dave

-----

Hi,

My solution is available here:

http://www.dave.burt.id.au/ruby/roman_n...

It can be used as a library (it pollutes String and Integer :) or as
required from the command line, filtering integers to roman numeral strings
and vice-versa.

An outline:

# Contains methods to convert integers to roman numeral strings and
vice-versa.
module RomanNumerals

# Maps roman numeral digits to their integer values
DIGITS = {

# The largest integer representable as a roman numerable by this module
MAX = 3999

# Stolen from O'Reilly's Perl Cookbook 6.23. Regular Expression Grabbag
REGEXP = /^M*(D?C{0,3}|C[DM])(L?X{0,3}|X[LC])(V?I{0,3}|I[VX])$/i

# Maps some integers to their roman numeral values
@@digits_lookup = DIGITS.inject({

# Converts +int+ to a roman numeral
def self.from_integer(int)
# main loop:
@@digits_lookup.keys.sort.reverse.each do |digit_value|
while remainder >= digit_value

# Converts +roman_string+, a roman numeral, to an integer
def self.to_integer(roman_string)
# main loop:
roman_string.to_s.upcase.split(//).reverse.inject(0) do |memo, digit|

# Returns true iif +string+ is a roman numeral.
def self.is_roman_numeral?(string)

class String
# Considers string a roman numeral numeral,
# and converts it to the corresponding integer.
def to_i_roman

# Returns true iif the subject is a roman numeral.
def is_roman_numeral?

class Integer
# Converts this integer to a roman numeral.
def to_s_roman

# Processes ARGF as per Quiz requirement - converts numbers to roman
numerals and vice versa
if __FILE__ == $0

Cheers,
Dave

5 Answers

James Gray

3/7/2005 2:54:00 PM

On Mar 7, 2005, at 8:04 AM, Dave Burt wrote:

> Hello mailing list. This has already been posted on Usenet, sorry for
> the duplication. (The gateway seems to be one-way at the moment.)

Thanks for copying it over here so I would see it, Dave. I went back
and browsed the newsgroup and picked up Timothy Byrd's solution as
well. That misbehaving gateway is hard on me. :D

James Edward Gray II

Dave Burt

3/8/2005 7:29:00 AM

"James Edward Gray II" <james@grayproductions.net>:
>> Hello mailing list. This has already been posted on Usenet, sorry for the
>> duplication. (The gateway seems to be one-way at the moment.)
>
> Thanks for copying it over here so I would see it, Dave. I went back and
> browsed the newsgroup and picked up Timothy Byrd's solution as well. That
> misbehaving gateway is hard on me. :D

Me too... having to join a hundred-plus-messages-per-day mailing list that
floods my mailbox just to submit my quiz solution... life's tough, isn't it?

Anyway, I have an update quiz-solution-wise.

I had a niggling feeling something was missing from my solution before I
submitted. And everyone else's once I'd read them all. And here it is:

# Enables uppercase roman numerals to be used interchangeably with integers.
# They are auto-vivified RomanNumeral constants
# Synopsis:
# 4 + IV #=> VIII
# VIII + 7 #=> XV
# III ** III #=> XXVII
# VIII.divmod(III) #=> [II, II]
def Object.const_missing sym
raise NameError.new("uninitialized constant: #{sym}") unless
RomanNumerals::REGEXP === sym.to_s
const_set(sym, RomanNumeral.get(sym))
end

Of course, this requires a RomanNumeral class, which acts like an Integer but
looks like a... well, roman numeral.

Go and download http://www.dave.burt.id.au/ruby/roman_n... again!

Cheers,
Dave

Brian Schröder

3/8/2005 10:38:00 AM

On Tue, 8 Mar 2005 16:29:11 +0900, Dave Burt <dave@burt.id.au> wrote:
> "James Edward Gray II" <james@grayproductions.net>:
> >> Hello mailing list. This has already been posted on Usenet, sorry for the
> >> duplication. (The gateway seems to be one-way at the moment.)
> >
> > Thanks for copying it over here so I would see it, Dave. I went back and
> > browsed the newsgroup and picked up Timothy Byrd's solution as well. That
> > misbehaving gateway is hard on me. :D
>
> Me too... having to join a hundred-plus-messages-per-day mailing list that
> floods my mailbox just to submit my quiz solution... life's tough, isn't it?
>
> Anyway, I have an update quiz-solution-wise.
>
> I had a niggling feeling something was missing from my solution before I
> submitted. And everyone else's once I'd read them all. And here it is:
>
> # Enables uppercase roman numerals to be used interchangeably with integers.
> # They are auto-vivified RomanNumeral constants
> # Synopsis:
> # 4 + IV #=> VIII
> # VIII + 7 #=> XV
> # III ** III #=> XXVII
> # VIII.divmod(III) #=> [II, II]
> def Object.const_missing sym
> raise NameError.new("uninitialized constant: #{sym}") unless
> RomanNumerals::REGEXP === sym.to_s
> const_set(sym, RomanNumeral.get(sym))
> end
>
> Of course, this requires a RomanNumeral class, which acts like an Integer but
> looks like a... well, roman numeral.
>
> Go and download http://www.dave.burt.id.au/ruby/roman_n... again!
>
> Cheers,
> Dave

That is a neat trick! Thanks a lot for sharing.

Regards,

Brian
--
Brian Schröder
http://ruby.brian-sch...

Martin DeMello

3/8/2005 11:09:00 AM

Dave Burt <dave@burt.id.au> wrote:
> def Object.const_missing sym

Wow - I never knew about const_missing! This language never ceases to
surprise me :)

martin

Florian Frank

3/8/2005 12:49:00 PM

Dave Burt wrote:

> Go and download http://www.dave.burt.id.au/ruby/roman_n... again!

Nice, now Ruby has them, too, like Perl did before. Small patch here:

--- roman_numerals.rb.1 Tue Mar 8 08:27:13 2005
+++ roman_numerals.rb Tue Mar 8 13:39:07 2005
@@ -135,7 +135,7 @@
else
to_i = value.to_s.to_i_roman
end
- @@all_roman_numerals[to_i] || RomanNumeral.new(to_i)
+ @@all_roman_numerals[to_i] || new(to_i)
end

def inspect

You can do funny things with those Roman numbers, BTW:

>> I += 1 ; I == II
(irb):1: warning: already initialized constant I
=> true

;)

--
Florian Frank

comp.lang.ruby

Re: [QUIZ] Roman Numerals (#22

Dave Burt

James Gray

Dave Burt

Brian Schröder

Martin DeMello

Florian Frank

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