OT: Re: Just took a look in the perl newsgroup....

[Steven Taschuk]

Quoth Bengt Richter:
> On Wed, 28 May 2003 14:17:37 -0600, Steven Taschuk <staschuk at telusplanet.net> wrote:
> >Quoth Bengt Richter:
  [...]
> >>         ## a local case structure with rebinding in local scope
> >>         try: raise `x`
> >>         except '1':
  [...]
> >Inherently fragile due to reliance on interning of repr(x).  Won't
> >work at all if/when string exceptions go away.
>
> Which version requires interning of repr(x)? It looks like the code is less
> efficient than the corresponding if/elif/else code, however.

It is the quoted try/except version that relies on interning.  For
example:

    >>> x = 12345
    >>> try:
    ...     raise `x`
    ... except '12345':
    ...     print 'case 12345'
    ... 
    Traceback (most recent call last):
      File "<stdin>", line 2, in ?
    12345

Because string exceptions are caught by identity, not equality,
and, as it happens, '12345' doesn't get interned.

  [...]
> class Switch(object):
>     def __init__(self, *caseNames):
>         for name in caseNames:
>             if not isinstance(name,str): name = `name`
>             exec ('class _%s(Exception):pass'%name) in self.__dict__
>             del self.__dict__['__builtins__']
>     def __call__(self, name):
>         raise getattr(self, '_%s'%name, ValueError)

Yikes again.  This one depends on repr(x) fitting into identifier
syntax, so I couldn't use it with tuples (to pick one example of
many).

  [...]
-- 
Steven Taschuk                                7\ 7'Z {&~         .
staschuk at telusplanet.net                        Y r          --/hG-
                                            (__/ )_             1^1`