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To: python-list@python.org
From: Terry Reedy <tjreedy@udel.edu>
Subject: Re: PyWart: More surpises via "implict conversion to boolean" (and other steaming piles!)
Date: Tue, 11 Feb 2014 12:57:24 -0500
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Xref: csiph.com comp.lang.python:65934

On 2/11/2014 11:19 AM, Travis Griggs wrote:
>
> On Feb 11, 2014, at 7:52 AM, Chris Angelico <rosuav@gmail.com> wrote:
>
>> So in that situation, the no-args call does make sense. Of course,
>> this is a call to a function that does take args, but it's accepting
>> all the defaults and providing no additional content. It's quite
>> different to actually define a function that mandates exactly zero
>> arguments, and isn't making use of some form of implicit state (eg a
>> closure, or maybe a module-level function that manipulates
>> module-level state - random.random() would be an example of the
>> latter). Syntactically, Python can't tell the difference between
>> "print()" and "foo()" where foo can never take args.
>
> So at this point, what I=E2=80=99m reading is that actually making a =E2=
=80=9Cno arg function=E2=80=9D is difficult, if we widen the semantics.

It is quite easy.

def f(): return 3  # or any other constant.

Chris said that useful functions in Python are (mostly) not really=20
niladic, which is equivalent to saying that niladic functions in Python=20
are (mostly) not really useful. They are a mainly a device in pure=20
function theory to have constants (True, False, 0, 1, ...) while also=20
having everything be a function (the 'pure' part).  Pure set theory uses =

its own tricks to make the same constants (and functions) be sets ;-).

--=20
Terry Jan Reedy