From: "Guy N. Hurst" <gnhurst@...>
Date: 2002-03-19T23:20:30+09:00
Subject: Re: Wanted: slick rubyesqe algorithm

Marko Schulz wrote:
> 
> On Tue, Mar 19, 2002 at 01:53:50PM +0900, Guy N. Hurst wrote:
> >
> > Here's my contribution:
> >
> > a.each_index{|i| if String===a[i] then a[i,2]=a[i]+a[i+1] while String===a[i+1] end}
> 
> That's nice. I would prefer a little bit more readable version:
> 
>   a.each_index do |i|
>     if String===a[i]
>       a[i,2]=a[i]+a[i+1] while String===a[i+1]
>     end
>   end
> 
> My eyes are not adapted to Module#===Object either, but if one is used
> to it, this looks like a nice shortcut to Object#type==Module.
> 
> I am always a little afraid to modify a structure I am iterating
> over. Different languages and libraries are differently robust
> concerning this. Is it generally OK to do this in ruby?
> 

Well, if the method were made to self-modify, it may be considered
dangerous and marked with '!' unless it is expected to modify
the structure, like Array#shift or #pop.

Here is a safer approach which uses a copy:

class Array
  def join_adjacent_strings
    a=self.dup
    a.each_index do |i|
      if String===a[i]
        a[i,2]=a[i]+a[i+1] while String===a[i+1]
      end
    end
    a
  end
end


As for whether it is generally ok, I think that depends on
your target audience. As for me, I regularly do so for the
power it offers. Of course, I also like making self-modifying
CGI scripts ;-)  To me, it is not so much a structure as it is
a piece of modeling clay. Ruby allows me to be artistic in
my programming, and that is one more reason I like ruby.


Guy N. Hurst