From: Wayne Scott <wscott@...>
Date: 2001-05-03T08:26:06+09:00
Subject: [ruby-talk:14557] Arggg Bitten by the block var scope feature!!!


I just spend a day debugging a elegant script that had this
function.

    #simplified for this discussion
    def fetch(arg2)
        # cheesy block to flush cache if it has gotten too big
     	if @cache.length > 200
  	    # one pass at flushing cache
	    @cache.dup.each do |arg2, file|       ## (1)
    		file.flush
    		@cache.delete arg2
    	    end
    	end
	unless @cache[arg2]			  ## (2)
	    @cache[arg2] = @cl.new(@arg1, arg2)
	end
	@cache[arg2]
   end

The bug is that at (1) the variable 'arg2' is not local to the block
like I was expecting, but was just a copy of the function parameter
'arg2'.  So when I hit the normal part of the function at (2) the
parameter is trashed if I happened to have executed (1).

This is a bad feature in a language that I am otherwise falling in
love with.

I had stopped reading this list for the last couple months.  Has there
been any progress in an alternative syntax for block variables that
have their own scope??

OK I feel better.  I wanted to be able to complain to someone.

-Wayne

BTW from an eariler message this week I can change this:

	unless @cache[arg2]
	    @cache[arg2] = @cl.new(@arg1, arg2)
	end
	@cache[arg2]

into this:

        @cache[arg2] ||= @cl.new(@arg1, arg2)