From: Josef 'Jupp' Schugt <jupp@...>
Date: 2005-03-24T07:17:02+09:00
Subject: Re: Any guides for good coding in Ruby?

Arfin wrote:
> 1234	=>	"1,234.00"

I only handle the non-obvious "1234.00" -> "1,234.00" part of the task
but that one for float and integer regardless of length and sign. The
only minor trick is using positive lookahead to extract the right digits
in the case of a string that represents a float. Note that the argument
is left unchanged if

- it is no string
- it neither matches /^[-+]?\d+\.\d+$/ nor /^[-+]?\d+$/

The latter means that no modification is done if exponential notation is
used. This is done on purpose because one would not expect colons in
such a notation.

Extending the algorithm to numbers with leading zeroes is left as an
exercise to the reader :->

Here is the HOW IT IS DONE:

def threepack(x)
   return x unless x.class == String
   if /^[-+]?\d+\.\d+$/.match(x)
     match  = /((\d\d\d)+)(?=\.)/.match(x)
   elsif /^[-+]?\d+$/.match(x)
     match  = /((\d\d\d)+)$/.match(x)
   end
   return x if match.nil?
   result = match.pre_match
   temp   = match[1]
   until temp.empty?
     result << ',' unless ['', '-', '+'].member?(result)
     result << temp[0..2]
     temp = temp[3..-1]
   end
   result << match.post_match unless match.post_match.nil?
   result
end

testdata =  [

               12345678,
               '08/15',
               '4711 Eau de Cologne',
               'Beethoven',
               '%d' %         1,
               '%d' %        12,
               '%d' %       123,
               '%d' %     1_234,
               '%d' %    12_345,
               '%d' %   123_456,
               '%d' % 1_234_567,

               '%d' %         -1,
               '%d' %        -12,
               '%d' %       -123,
               '%d' %     -1_234,
               '%d' %    -12_345,
               '%d' %   -123_456,
               '%d' % -1_234_567,

                '%4.2f' %         1.0,
                '%5.2f' %        12.0,
                '%6.2f' %       123.0,
                '%7.2f' %     1_234.0,
                '%8.2f' %    12_345.0,
                '%9.2f' %   123_456.0,
               '%10.2f' % 1_234_567.0,

                '%5.2f' %         -1.0,
                '%6.2f' %        -12.0,
                '%7.2f' %       -123.0,
                '%8.2f' %     -1_234.0,
                '%9.2f' %    -12_345.0,
               '%10.2f' %   -123_456.0,
               '%11.2f' % -1_234_567.0,

             ]

testdata.each{|x| puts threepack(x)}

Here is the WHAT IS DONE:

12345678
08/15
4711 Eau de Cologne
Beethoven
1
12
123
1,234
12,345
123,456
1,234,567
-1
-12
-123
-1,234
-12,345
-123,456
-1,234,567
1.00
12.00
123.00
1,234.00
12,345.00
123,456.00
1,234,567.00
-1.00
-12.00
-123.00
-1,234.00
-12,345.00
-123,456.00
-1,234,567.00

Before someone asks: The examples were not chosen by chance; I live in
the former FRG capital of Bonn where Beethoven was born that is located
near Cologne.

Josef 'Jupp' Schugt
-- 
This space is intentionally left void.