Regex: move minus sign to front for negative numbers w trailing " -"

Hi cool rubyers:

I’m sorry but my little brain is stuck w my first ruby program. The
program’s objective is to move the “-” sign of negative numbers to the front
;eg, fr 999.99- to -999.99

so I run:
C:\family\ruby>ruby negatives.rb negatives.txt

and the output is:
99.99- 9999- 99-99 99-99- 99999.99- 9.99-

-99.99<< >>-9999<< >>-99<<99 >>-99<<>>-99<<
-99999.99<< >>-9.99<<

My program (regex actually) works for figures even of the form 9999-999 or
99-99-. I do NOT want this since these numbers may be dates, telno, etc…
So how do I restrict my regex so that it will only process numbers of the
form 999- or 999.99- but not 999-999 or 999-99-

the file contents of negatives.rb and negatives.txt follow below.

Many thanks for the help,
-botp w small brain…

···

#-------------------
#negatives.txt
99.99- 9999- 99-99 99-99- 99999.99- 9.99-

#-------------------
#negatives.rb
File.open(ARGV[0]) do |f|
f.each do |line|
puts line
puts (line.gsub ( /(\b)((\d+)|(\d+.\d+))(-)/,
’>>\5\1\2<<’))
puts
end
end

99.99- 9999- 99-99 99-99- 99999.99- 9.99-

It really depend on what you want : for a regexp the most difficult task
is the specification. When you have a *complete* specification, then you
can try to write it. For example I've added some cases

pigeon% cat b.rb
#!/usr/bin/ruby
DATA.each do |line|
   puts line
   puts line.gsub(/(^|[^-.\d])(\d+(?:\.\d+)?)-(?=[^-.\d]|$)/,'>>\1-\2<<')
   puts
end
__END__
99.99- 9999- 9.- .99- -99.99- 9.9-. 99-99 99-99- 99999.99- 9.99-
pigeon%

pigeon% b.rb
99.99- 9999- 9.- .99- -99.99- 9.9-. 99-99 99-99- 99999.99- 9.99-

-99.99<< >> -9999<< 9.- .99- -99.99- 9.9-. 99-99 99-99- >> -99999.99<< >> -9.99<<

pigeon%

Guy Decoux

Hello –

  puts (line.gsub ( /(\b)((\d+)|(\d+\.\d+))(-)/,

‘>>\5\1\2<<’))

I don’t know why I bother trying to hammer out answers to questions
like this when it’s still daylight in Paris… :slight_smile: but anyway, I just
wanted to make one observation, for possible future reference.

Namely: there’s no point capturing a \b match and backreferencing it,
because it’s just a zero-width assertion. It doesn’t actually match
or consume a character in the string; it’s just a constraint on the
upcoming attempted match.

David

···

On Sat, 27 Jul 2002, [iso-8859-1] “Peña, Botp” wrote:


David Alan Black
home: dblack@candle.superlink.net
work: blackdav@shu.edu
Web: http://pirate.shu.edu/~blackdav