From: "Derrick B." <lists@...>
Date: 2012-12-22T03:19:09+09:00
Subject: Re: Perl to Ruby: regex captures to assignment.

Robert Klemme wrote in post #1089807:

> That was just for demonstration purposes.
>

Understood.

>
> There's still a better way to do that then just match everything non
> whitespace.  How would you parse ":s9d2++*3h43" as a number?
>
> ["1 3/4", "5", '-23', '-23 -4/4'].each do |s|
>   puts s
>
>   if %r{\A([-+]?\d+)(?:\s+([-+]?\d+)/(\d+))?\z} =~ s
>     w, n, d = $2 ? [$1.to_i, $2.to_i, $3.to_i] : [1, $1.to_i, 0]
>     printf "%4d %4d %4d\n", w, n, d
>   else
>     $stderr.puts "No match #{s}"
>   end
> end
>

I like that, because it introduces to_i during capture, which was what I
was also trying to figure out.  I have already modified my regex to
something similar to yours.

> Btw, did I mention that I find your variable assignment weird?  I'd
> rather do
>
> ["1 3/4", "5", '-23', '-23 -4/4'].each do |s|
>   puts s
>
>   if %r{\A([-+]?\d+)(?:\s+([-+]?\d+)/(\d+))?\z} =~ s
>     w, n, d = $2 ? [$1.to_i, $2.to_i, $3.to_i] : [$1.to_i, 0, 1]
>     printf "%4d %4d %4d\n", w, n, d
>   else
>     $stderr.puts "No match #{s}"
>   end
> end
>

I will have to search for "weird" in recent posts.  haha!  I do not
doubt it, but for my C++ to Perl to Ruby translation, it was
seamless.

> I don't have the time right now but you should definitively use class
> Rational.  Also your parsing of the command line could be better:
>
> do
>   print "Fraction 1: "
>   input = gets or break
>   f1 = parse_fraction(input)
>
>   print "Fraction 2: "
>   input = gets or break
>   f2 = parse_fraction(input)
>
>   print "Command: "
>   input = gets or break
>
>   case input
>   when "A"
>     puts f1 + f2
>   when "S"
>     puts f1 - f2
>  ...
>  else
>    abort "Invalid command: #{input}"
>  end
>
> end until cmd == "Q"
>
> puts "Quitting"
>
>
> You should also not implement #to_string but rather #to_s and then use
> string interpolation for constructing your outputs.
>
> Kind regards
>
> robert

As I stated as an edit in a previous post, this started as an assignment
to create a C++ class that handles fractions, so I then created a Perl
"class", and now a Ruby class.  So, using "require rational", or "use
bigrat" in Perl, would have defeated the purpose.  I do plan on learning
more about Ruby, and Perl, add-ons.

Thank you all for the input!  I really appreciate being able to post
code and have quality responses.  I am transitioning from a career
(nearly 20 years) in IT, to going to school to get my BS in CS, to then
continue as a programmer.

I'll try not to be a stranger as long as my code is to be considered
strange.  :)

-- 
Posted via http://www.ruby-forum.com/.