[Python-Dev] Recommend accepting PEP 312 -- Simple Implicit Lambda

[Josiah Carlson]

Kay Schluehr <kay.schluehr at gmx.net> wrote:
> Maybe anonymus function closures should be pushed forward right now not 
> only syntactically? Personally I could live with lambda or several
> of the alternative syntaxes listed on the wiki page.

> But asking for a favourite syntax I would skip the "def" keyword from 
> your def-arrow syntax proposal and use:
> 
>     ((a, b, c) -> f(a) + o(b) - o(c))
...

> The arrow is a straightforward punctuation for function definitions. 
> Reusing existing keywords for different semantics seems to me as a kind 
> of inbreeding.

That's starting to look like the pseudocode from old algorithms
textbooks, which is very similar to bad pseudocode from modern CS theory
papers.  Punctuation as a replacement for words does not always win
(perfect examples being 'and' vs. &&, 'or' vs. ||, 'not' vs. !, ...)

-1 on the syntax offering.

> For pushing anymus functions forward I propose to enable explizit 
> partial evaluation as a programming technique:

If I remember correctly, we've got rightcurry and leftcurry for that (or
rightpartial and leftpartial, or something).

>  >>> ((x,y) -> (x+1)*y**2)
> ((x,y) -> (x+1)*y**2)
> 
>  >>> ((x,y) -> (x+1)*y**2)(x=5)
> ((y) -> 6*y**2)

I'll assume that you don't actually want it to rewrite the source, or
actually return the source representation of the anonymous function
(those are almost non-starters).

As for all anonymous functions allowing partial evaluation via keywords:
it would hide errors.  Right now, if you forget an argument or add too
many arguments, you get a TypeError.  Your proposal would make
forgetting an argument in certain ways return a partially evaluated
function.

-1 on partial evaluation.


 - Josiah