On Wed, May 13, 2009 at 7:08 PM, Terry Reedy tjreedy@udel.edu wrote:
Bruce Leban wrote:
Here's what I'd like:
def myfunc(a, b, c = *lambda: expression): stuff
The use of the lambda keyword here makes the scope of any variables in the expression clear. The use of the prefix * makes the syntax invalid today, suggests dereferencing and doesn't hide the overhead. This is equivalent to:
There is a proposal, which I thought was accepted in principle, to make '* seq' valid generally, not just in arg-lists. to mean 'unpack the sequence'.
- (lambda:1,2)() would then be valid, and without the call, would be a
runtime, not syntax error.
Other than that ;0(, it would be an interesting idea.
Then how about putting the * before the parameter ?
def myfunc(a, b, *c = lambda: expression):
It's currently a syntax error, although the fact that "*arg" and "*arg=default" would mean something completely different is problematic. Still the same idea can be applied for some other operator (either valid already or not).
Regardless of the actual operator, I came up with the following additional subproposals.
Subproposal (1): Get rid of the explicit lambda for dynamic arguments. That is,
def myfunc(a, b, *x=[]):
would be equivalent to what previous proposals would write as
def myfunc(a, b, *x=lambda: []):
Subproposal (2): If subproposal (1) is accepted, we could get for free (in terms of syntax at least) dynamic args depending on previous ones. That is,
def myfunc(a, b, *m=(a+b)/2):
would mean
def myfunc(a, b, *m = lambda a,b: (a+b)/2):
with the lambda being passed the values of a and b at runtime.
Thoughts ?
George