[Python-ideas] Proposal for function expressions

[MRAB]

Chris Perkins wrote:
> On Tue, Jul 14, 2009 at 7:41 AM, Carl
> Johnson<cmjohnson.mailinglist at gmail.com> wrote:
>> This idea seems to be almost identical to my thread from November,
>> "Proposal for Ruby-style anonymous block functions      (that don't kill
>> the indention)":
>> http://mail.python.org/pipermail/python-ideas/2008-November/002340.html
> 
> Cool! I had not seen that thread, but the fact that you and I have
> proposed nearly the same thing independently increases the odds that
> I'm not just nuts. :)
> 
>> The real difference is that your proposal uses & (which is a bad idea,
>> since & already has a meaning: __and__) and in
>>
>> foo() do:
>>   BODY
>>
>> it implicitly injects the BODY function into the args of foo, which
>> violates Explicit Is Better Than Implicit.
> 
> I considered the use of a "magic" placeholder character to be an
> unfortunate but necessary evil - the alternative seemed to be to
> restrict the block/def-expression to becoming the last argument to the
> function call that it follows, and that was just too restrictive. I
> have no particular attachment to "&" - but note that there is no
> ambiguity with the bitwise and operator, as far as I can tell. Eg.
> this works:
> 
>>>> def f(a): return a()
> ...
>>>> 3 & f(&) do: return 5
> 1
> 
> (not that you would write real code like that...)
> 
[snip]

Another possibility is to permit a local name (it's not an anonymous
function any more!) so that you can have multiple functions:

3 & f(foo) def foo:
     return 5

3 & f(foo, bar) def foo, bar:
     return 5
and:
     return 6

Anyway, how would you handle condition expressions, as used in 'if' and
'while' statements? /They/ also expect a terminating colon and an
indented block.