Label-Value (was: Re: Inheriting the @ sign from Ruby)

[Rainer Deyke]

"Alex Martelli" <aleaxit at yahoo.com> wrote in message
news:91d5el0me7 at news1.newsguy.com...
> "Rainer Deyke" <root at rainerdeyke.com> wrote in message
> news:rWd_5.26820$x6.14119694 at news2.rdc2.tx.home.com...
>     [snip]
> > > > class MutableInt(UserInt.UserInt):
> > > >   def set(self, value):
> > > >     self.data = value
> > >
> > > UserInt is not in the Python 2 docs, though it's nice to hear it
> > exists:-).
> >
> > Actually it doesn't, but it's trivial (if tedious) to implement.
>
> But, if UserInt is not a funky metaclass, how will MutableInt live
> up to its name?  Surely it should at least redefine all of the
> in-place methods...:
>
>     x = y = MutableInt(23)
>     x += 1

Yes, in-place modification should be supported.  I had something like this
in mind:

class UserInt:
  def __init__(self, value):
    self.data = value
  def __add__(self, other):
    if isinstance(other, UserInt):
      return self.__class__(self.data + other.data)
    else:
      return self.__class__(self.data + other)
  __radd__ = __add__
  def __iadd__(self, other):
    if isinstance(other, UserInt):
      self.data += other.data
    else:
      self.data += other
  # Repeat for all other operations

UserInt as written is more properly UserNumber, since it supports longs ints
and floats.


--
Rainer Deyke (root at rainerdeyke.com)
Shareware computer games           -           http://rainerdeyke.com
"In ihren Reihen zu stehen heisst unter Feinden zu kaempfen" - Abigor