From: Robert Klemme <bob.news@...>
Date: 2003-03-17T18:21:04+09:00
Subject: Re: Ruby / Eiffel ?


"Jason M Jurkowski ;002;icsg6;" <jmj8237@cs.rit.edu> schrieb im
Newsbeitrag news:Pine.GSO.4.53.0303132238200.20279@utah.cs.rit.edu...
> i've coded up a ruby "assertion" for myself as follows:
>
> def assert(conditional)
>   begin
>     raise Exception, "assertion failed" if not conditional
>   rescue Exception => e
>     filename = e.backtrace()[1].split(/:/)[0]
>     lineno = e.backtrace()[1].split(/:/)[1].to_i()
>     file = File::new(filename)
>     puts e.message+": "+file.readlines()[lineno-1]
>     exit! 1
>   end
> end

Throwing and immediately catching an exception is superfluous. I like
this more:

def assert(cond)
  unless cond
    filename, lineno = caller[0].split(/:/)
    raise ( File.open( filename ) do |f|
      "assertion failed at #{filename}:#{lineno}: #{ f.readlines()[
lineno.to_i - 1 ] }"
    end )
  end
end

Note that the exception trace that ruby prints for uncaught exceptions
does contain the file and line number already.  So if you leave out
printing of the line itself, this is sufficient:

def assert(cond)
  raise "assertion failed" unless cond
end

And for delivered code

def assert(cond); end

regards

    robert