From: ts <decoux@...>
Date: 2004-04-21T22:03:37+09:00
Subject: Re: Ruby proposal: MAIN_BINDING

>>>>> "D" == Dan Doel <djd15@po.cwru.edu> writes:

D> The issue (as I understand it), is that #eval opens up a new scope

 Well, not really. The problem is this is at *compile* time that ruby make
 the difference between a variable and a method

 When you write

      eval("a = 'hello'",MAIN_BINDING)
      puts a

 ruby at compile time see a string and the statement

      puts a

 which is interpreted as

      puts a() # method call because no local variable with the name `a'
               # was defined

 and you can't change this, just imagine

     def tt(str)
        eval(str)
        puts a
     end

     tt("a = 'hello'")
     tt("b = 'hello'")

 ruby will not be able to see, that *latter* the method #tt will be called
 with "a = 'hello'", and in this case `a' can be a local variable.

 Just imagine that ruby read line from a file and then call the method #tt
 with these lines.

 Worst and perhaps I've forgotten to say it : eval is evil


Guy Decoux