On 03/03/17 19:02, Alexandre Brault wrote:
I believe what Matthias is hoping for is an equivalent of Java's named
break feature. Breaking out of an outer loop implicitly breaks out of
all inner loops
Yes, and although I think making this a runtime object is an interesting
thought (in terms of perhaps allowing other funky stuff to be
implemented by a custom object, in line with Python's general dynamic
ethos), I think that it should perhaps be considered a lexer/parser
level thing only.
* Creating a real object at runtime for each loop which needs to be the
target of a non-inner break or continue is quite a large overhead. How
would this affect Python variants other than CPython?
* For anything "funky" (my words, not yours ;)), there needs to be a way
of creating a custom loop object - what would the syntax for that be? A
callable needs to be invoked as well as the name bound (the current
suggestion just binds a name to some magical object that appears from
somewhere).
* If nothing "funky" needs to be done then why not just make the whole
thing syntax-only and have no real object, by making the 'as' name a
parser-only token which is only valid as the optional subject of a break
or continue statement:
for foo in bar as LABEL:
. # (a)
.
for spam in ham:
.
.
if eggs(spam):
continue LABEL
.
.
if not frob(spam):
break LABEL
# (b)
(a) is the code generator's implied 'continue' target for the LABEL loop.
(b) is the code generator's implied 'break' target for the LABEL loop.
I'm not saying that's a great solution either. It's probably not an
option as there is now something that looks like a bound name but is not
actually available at runtime - the following would not work:
for foo in bar as LABEL:
print(dir(LABEL))
(and presumably that is part of the reason why the proposal is the way
it is).
I'm generally +0 on the concept (it might be nice, but I'm not sure
either the original proposal or what I mention above are particularly
problem-free ;)).
E.
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