From: Per Bothner <per@bothner.com>
To: kawa@sourceware.org
Subject: Re: APL-style array indexing in Kawa - a sketch
Date: Tue, 18 Aug 2015 04:12:00 -0000 [thread overview]
Message-ID: <55D2B087.2020506@bothner.com> (raw)
In-Reply-To: <112A4F9C-EF11-4386-B0DC-BA93C01A9CA0@theptrgroup.com>
On 08/17/2015 08:37 PM, Jamison Hope wrote:
> On Aug 17, 2015, at 6:47 PM, Per Bothner <per@bothner.com> wrote:
>
>> We could define [<:] as a supported syntax (see $bracket-list$ in syntax.scm).
>> It would be relative easy to define 0 as the default lower bound, but that
>> doesn't quite do what you want. We could define [<;] as a special magic value
>> that gets coerced to a specific range depending on context.
>
> Hmm can we pick something that won't confuse paredit mode?
I'm not familiar with paredit - but why would [<:] confuse it?
> (array-map (lambda (x) (* 2 x)) ARR) => a new array where each element
> is doubled in value.
>
> (array-map + ARR1 ARR2) => a new array representing the elementwise sum
> of the elements of ARR1 and ARR2.
>
> (I'm imagining that the array-map call wouldn't allocate a new data
> buffer, but would just close over the supplied function and array(s),
> lazily applying the function to array elements as needed.)
"Lazily" is confusing here. I think array-map should eager, in the
same way vector-map is. What it should do:
(1) Figure out the shape of the result. (The same as the argument, if
a single argument; otherwise they may be "broadcast" in the Racket sense.)
(2) Allocate an Object[] buffer for the result whose length is the
element-count of the shape.
(3) Iterate of the shape (which is the same as iterating over the buffer);
extract the corresponding argument array value using the same (or broadcast)
indexes; call the function.
http://docs.racket-lang.org/math/array_pointwise.html
The Racket array functions is another place to look for inspiration.
--
--Per Bothner
per@bothner.com http://per.bothner.com/
next prev parent reply other threads:[~2015-08-18 4:12 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-08-14 1:59 Per Bothner
2015-08-17 20:24 ` Jamison Hope
2015-08-17 22:48 ` Per Bothner
2015-08-18 3:37 ` Jamison Hope
2015-08-18 4:12 ` Per Bothner [this message]
2015-08-18 4:43 ` Jamison Hope
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