From: Gunnar Andersson <dff180@...>
Date: 2002-02-13T08:40:04+09:00
Subject: Re: [newbie] make first letter lowercase

Hi everyone!

Cool ideas with the parts/expose...

Some discussion points:

I think Matju's original Part, or Slice or Fragment
are reasonable names and maybe it's good to clarify 
that it doesn't return a String but something different.  
I used expose() below but the names part(), slice() 
or fragment() tell you what you actually get back.

Because if you consider that side of it, you would
be inclined to actually handle the return value of 
expose/part/fragment.  

But I'm not sure it's a good thing after all. 
(Arguing with myself for a while...) because
a ref to this thing is powerful but a little
scary.  It's like having a pointer into the middle of 
a C-string that you use later on - I mean I would
find such code harder to understand and debug, you
see what I mean?

The other way, the name expose() doesn't really
tell you what you get back and instead suggests the user 
to use it in that manner: 
expose().something! 
which might be a good thing if it can avoid proliferation 
of these "dangerous" Fragment objects which effectively alias 
(part of) the original object.

I guess what I'm saying is that such simple things like
the actual names of things can affect people's use of 
these features and, basically, their coding style.
You give people powerful tools and they get crazy
ideas! ;-)  But I'm not your mommy so why should I 
care?

To conclude, I see advantages and disadvantages with both 
types of names.  What do you think?


OK, so just for fun, here's a first attempt at a Ruby hack to 
do it.  I love it when Ruby just makes it possible.  
While it isn't always the nicest solutions, at least
everyone can play around with it to get the feel for it without
any hacking/recompile of the interp.  It's based on 
a method_missing hack like so many other such tricks.
(What did I say about providing powerful stuff in the 
language? :-)

Lots to improve I'm sure...
It now returns the result of the operation, not self so you 
can't chain operations. Actually if method_missing returned 
self instead it should work, but there are some other problems 
I see.  I think it'll bug out if the first op returns a longer 
string than the original fragment (the range is not reset to
the longer length), and so on.
Should be possible to fix something though...

Later...

/Gunnar

----

class String
   def expose(range)
      @range = range
      Fragment.new(self, range)
   end
   def expose_result(s)
      self[@range] = s
   end
end

class Fragment 
   def initialize(string, range)
     @string = string 
     @range = range
   end

   def method_missing(m, *args)
      s = @string[@range]
      retval = s.send(m, *args)
      @string.expose_result(s)
      retval
   end
   def inspect; "\"#{@string[@range]}\""; end
end

# Try it out:

s2 = "The quick brown fox"
fragment = s2.expose(4..8)  # >> "quick"
p fragment         
p fragment.upcase  # >> "QUICK"
p s2               # >> "The quick brown fox"
fragment.upcase!   # >> "QUICK", also affects s2
p s2               # >> "The QUICK brown fox"

# Substitute within fragment only 
s1 = "The quick quick quick brown fox"
s1.expose(10..20).gsub!(/quick/, "slow") # >> "The quick slow slow..."
p s1

s = "No    squeezing   here. But here: -X  X    X   X      X  X-"
p s
s.expose(34..-1).squeeze!(" ")
p s



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