[swift-evolution] higher kinded types vs Python's syntactic sugars

[T.J. Usiyan]

That is… damned nice. I choose not to feel that bad about it… for reasons.



On Fri, Dec 18, 2015 at 8:04 PM, Dave Abrahams <dabrahams at apple.com> wrote:

>
> On Dec 18, 2015, at 4:35 AM, Al Skipp via swift-evolution <
> swift-evolution at swift.org> wrote:
>
> On 18 Dec 2015, at 00:19, T.J. Usiyan via swift-evolution <
> swift-evolution at swift.org> wrote:
>
> With a Cartesian Product type [like this](
> https://github.com/griotspeak/CartesianProduct), the for-in-where syntax
> actually gets us to list comprehensions. I'll admit that I might not have
> implemented the best Cartesian Product type possible, but it should
> illustrate that we have what we need.
>
> `for case … in cartProd(cartProd(seq1, seq2), seq3) // An operator for
> cartProd would make it more pleasing to read.`
>
>
> That’s impressive work, but it strikes me as quite a difficult undertaking
> to get there. (Is it just me, or are generators and sequences the most
> scary part of Swift?) Also, is it possible to get it working as an
> expression, or is it restricted to a ‘for’ statement? If it can only be
> performed as a ‘for’ statement it will still need an external mutable var
> to be updated outside of the loop. It’s fine if you want to just do
> side-effecty things, like print the elements, but I’d consider the ability
> to return a value to be more important.
>
>
> This is a much simpler cartesian product implementation:
>
>    seq1.flatMap { x in seq2.map { (x,$0) } }
>
> or, if you want speed,
>
>    seq1*.lazy*.flatMap { x in seq2*.lazy*.map { (x,$0) } }
>
> HTH,
>
> -Dave
>
>
>
>
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