[Python-ideas] Rehabilating reduce (as "fold")

[Haoyi Li]

> https://github.com/lihaoyi/macropy#quick-lambdas

Yeah I'm the author of that =D

My point wasn't so much that "use my cool macroz!!!" as "passing operator
as string PHP-style makes me sad =(" and with examples of how other
languages do it that doesn't make me sad.




On Fri, Jul 12, 2013 at 7:58 PM, Joshua Landau <joshua at landau.ws> wrote:

> On 12 July 2013 11:36, Haoyi Li <haoyi.sg at gmail.com> wrote:
> > I'd be all for increasing usage of fold and reduce, and higher order
> > combinators in general, but wasn't it always a somewhat philosophical
> issue
> > that kept lambdas intentionally verbose/crippled and discouraged usage of
> > Higher-Order-Functions when direct imperative code (i.e. loops) works?
> I've
> > always felt reduce() being banished was but a small facet of this overall
> > philosophy, and not so much because it was individually difficult to use.
> >
> >> data = fold("+=", [], iterables)
> >
> > Seems like a terrible hack to me =( it brings back memories of my PHP
> days
> > where "first class functions" meant you passed in the functions name as a
> > string which got concatted-around and eval-ed. We all laughed at how
> badly
> > they designed the language to have it end up like that. Naturally, it is
> the
> > path of least resistance, since it could be implemented with existing
> > language features (i.e. `eval`, which can implement anything really) but
> it
> > would leave a sour taste in my mouth every time i use it.
> >
> > I would much prefer the somewhat-more-difficult route of modifying the
> > parser to let `a += b` be an expression, and then you could write
> >
> > data = fold(lambda a, b: a += b, [], iterables)
> >
> > or even groovy/scala/mathematica style
> >
> > data = fold(_ += _, [], iterables)
> >
> > Which is a lot further (implementation wise) from where we are now, and 2
> > characters more verbose, but it would be far more generally usable than a
> > one-off "let's pass in operators as strings and concat/eval them" rule.
>
> https://github.com/lihaoyi/macropy#quick-lambdas
>
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