From: Phillip Gawlowski <pg@...>
Date: 2009-12-31T20:06:27+09:00
Subject: Re: Why can't I use "or" here?

On 31.12.2009 11:38, Albert Schlef wrote:

> What do you mean?

Something like this:
PS C:\Scripts> ruby .\unless.rb
we had an argument error
PS C:\Scripts> ruby .\unless.rb arg
arg
PS C:\Scripts> cat .\unless.rb
begin
   raise  ArgumentError unless ARGV[0]
   puts ARGV[0]
rescue ArgumentError
   puts "we had an argument error"
end

Basically, the begin/rescue/end tokens (bits that Ruby understands 
without being told about by you) allow the programmer to recover from an 
error in a graceful way.

If you had a file open, for example, you can make sure it is closed 
properly if a so-called exception (Like ArgumentError in the example) 
appears.

--
Phillip Gawlowski