declaration of variables?

[Paul Rubin]

Laura Creighton <lac at strakt.com> writes:
> Am I understanding you correctly?  You don't want to bind a variable
> to a specific type, and you want to be able to rebind a variable at
> will to any other type, but you want a language change so that the
> first time you bind a variable, you have to type something extra
> indicating 'yes I know this is the first time I have used this
> variable?'  If so, what does this buy you aside from catching typos?

For one thing, it lets you tell reliably whether a variable is global
or local.  Consider this code, which sets a global and then uses its
value in the middle of a complicated function (example due to Andrew Koenig):

   x = 3   # global variable

   def f():
      [some code]
      if frob():
         y = x        # sets y to 3 
      [more code]
      [still more code]

Now you edit the function for some reason:

   def f():
      [some code]
      if frob():
         y = x        # oops!!!
      [more code]
      x = 5
      [still more code]

Adding the "x = 5", possibly hundreds of lines into the function, has
changed x from a local into a global, so the "y = x" now does
something completely different from previously.

Catching typos is also perfectly worth doing.   See for example the
"use strict" feature in perl.