[Python-ideas] Query about proposed Multi-line Anonymous Function syntaxes

[Adam Jorgensen]

On 10 October 2014 20:42, Guido van Rossum <guido at python.org> wrote:

> On Fri, Oct 10, 2014 at 8:06 AM, Adam Jorgensen <
> adam.jorgensen.za at gmail.com> wrote:
>
>>
>> So, as I understand it, the main reason we don't have multi-line
>> anonymous functions is because there has been no consensus about
>> the syntax.
>>
>
> Well, it's worse -- it's hard to propose a syntax that actually works
> without huge changes to the way Python's parser treats indentation: inside
> parentheses, indentation is currently *not* significant.
>

Aaaaaah, this was exactly the area I figured would be an issue when I
thought about the problem for more than 10 seconds :-)


>
>
>> I was just wondering if someone has a document detailing the various
>> syntaxes that have been proposed in the the past.
>>
>
> No, but there have been many discussions. If you have a taste for mailing
> list archaeology it would be nice of you could dig up the various threads
> and summarize them for posterity, so at least we might make progress rather
> than going around in circles.
>
> As for myself, I have encountered a number of languages that do support
> multi-line anonymous functions (Java, JavaScript, CoffeeScript) and I have
> to say that for some reason they do not lead to very readable code.
> Especially in the latter two, the prevalent use for anonymous functions is
> for asynchronous I/O callbacks. I find Python 3.4's "yield from" as used by
> the asyncio library leads to much more readable code, without he need for
> callback functions at all.
>

I agree that anonymous functions do have the potential to produce illegible
code, although I think this might be more a product of those languages
general ability to enable said illegibility :-)

In the context of python the only strong use-case I personally have for
anonymous functions is a (extant) scenario where I'm writing nested
decorators that don't use the decorator package to preserve signatures
(There are some instances where signature preservation is actually
undesirable :-). In this scenario the nested defs *might* be cleaner
written in using anonymous functions, although there's no guarantee and
it's not exactly a common scenario anyway...

Maybe if I have some time I'll do the archaeology and cobble together a
summary of the various proposals...

>
> --
> --Guido van Rossum (python.org/~guido)
>
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