control structures (was "Re: Sins")

[Emile van Sebille]

Doesn't this do that now? or is there some objection to this usage?

for i in range(3):
  try:
    elem = "... nested loops & stuff ..."
    if i < 2:
      raise "element found", elem
    "... more stuff ..."
    raise "search failed"
  except "element found", e:
    print "Found", e
  except "search failed":
    print "Not Found"
  print 'looping on i=%d' % i
print 'e-o-f'


Found ... nested loops & stuff ...
looping on i=0
Found ... nested loops & stuff ...
looping on i=1
Not Found
looping on i=2
e-o-f
Process completed successfully

maybe-I'm-missing-the-obvious?-ly y'rs

Emile van Sebille
emile at fenx.com
-------------------



Evan Simpson <evan at tokenexchange.com> wrote in message
news:<s76uc120hu870 at corp.supernews.com>...
> Steve Holden <sholden at bellatlantic.net> wrote in message
> news:387358BB.E71EC4E7 at bellatlantic.net...
> > Phil Jensen wrote:
> > >     loop until "element found" or "search failed":
> > >         ...
> > >         if blah1 == blah2:
> > >             "element found"
> > >         ...
> > >     when "element found":
> > >         ...
> > >     when "search failed":
> > >         ...
>
> I proposed a spelling for this a while back, and have even made
sporadic
> forays into the Python source to see if I can implement it myself.  It
> extends 'try', and would look like this:
>
> try:
>     ... nested loops & stuff ...
>            break "element found", elem
>     ... more stuff ...
>         break "search failed"
> continue "element found", e:
>     print "Found", e
> continue "search failed"
>     print "Not Found"
>
> > Typically one would use enumerations rather that strings to
> > represent the loop states, to combine readability with efficiency.
>
> In this syntax, the strings are treated as labels (despite being
string
> literals grammatically) and are purely static, for both efficiency and
> error-checking.  That is, "break STRING, exprlist" is a compile-time
> SyntaxError unless the string exactly matches the string in a
"continue"
> clause of an enclosing "try" and the expression list is
> assignment-compatible with the argument list of that same clause.
Once this
> matching is done, the string is discarded and the "break" converted
into an
> expression evaluation followed by a Jump.  "continue" clauses compile
into a
> Jump to the end of the "try" followed by an assignment LHS (the target
of
> the "break" Jump) and the suite body.
>
> In many ways this is quite similar to raising an exception and
catching it
> in an "except" clause.  The major difference is that everything is
totally
> resolved at compile time, and is lexically fixed.
>
> > > Whatever the loop is, its exit or exits have some "meaning"
> > > in the program, and this control structure encourages an
> > > element of Literacy by forcing them to be named.
>
> Exactly.  With no penalty in speed or (compiled) code size, in this
case.
>
> Cheers,
>
> Evan @ 4-am
>
>
> --
> http://www.python.org/mailman/listinfo/python-list
>
>