Hey cycl...@speakeasy.net,
Jay's excellent main point is really about the use of anonymous functions-
that in many cases it's an anti-pattern.
Having a name for every function means that those functions become testable
and that code consuming those functions stays readable.
Another point is that core has a lot of functionality and especially when
one is new to the functional mindset, it's easy to miss something that
makes your job easy.
There will be many ways of expressing a particular operation, and it's
worth trying a few different ways to get to the semantics that make most
sense.
Here's one suggestion- turn the anonymous function into a named function
and use partial to compose the rule you need:
(defn quad-piece?
[row col piece]
(and (= row (:quad-row piece))
(= col (:quad-col piece))))
(defn get-quad-pieces
[galaxy [row col]]
(filter (partial quad-piece? row col) galaxy))
Then maybe it looks like get-quad-pieces isn't doing very much and maybe
there are some filter cases to capture instead:
(def zeros (partial quad-piece? 0 0))
(filter zeros test-galaxy)
Anyway, hope that's helpful.
Jonah
On Wed, Jan 27, 2016 at 8:19 PM, <cycl...@speakeasy.net> wrote:
> (def test-galaxy [{:quad-col 0, :quad-row 0, :sec-row 4, :sec-col 4, :type
> :E}
> {:quad-col 0, :quad-row 0, :sec-row 4, :sec-col 3,
> :type :base}
> {:quad-col 3, :quad-row 5, :sec-row 7, :sec-col 5,
> :type :star}
> {:quad-col 1, :quad-row 3, :sec-row 0, :sec-col 5,
> :type :klingon}])
>
> (defn get-quad-pieces
> [galaxy [quad-row quad-col]]
> (let [quad-pieces (filter (fn [elem] (and (= (:quad-row elem) quad-row)
> (= (:quad-col elem)
> quad-col))) galaxy)]
> quad-pieces))
>
> (get-quad-pieces test-galaxy [0 0])
> ; ({:quad-col 0, :quad-row 0, :sec-row 4, :sec-col 4, :type :E} {:quad-col
> 0, :quad-row 0, :sec-row 4, :sec-col 3, :type :base})
>
>
> Jay Fields makes an excellent argument for using core functions, instead
> of anonyous functions, wherever possible
> http://blog.jayfields.com/2012/10/clojure-avoiding-anonymous-functions.html
> In his example, he was grouping elements, not filtering by multiple
> values, which is what I'm trying to do.
>
> I'm trying to refactor one particular piece of code, and have no idea
> what, if any, core functions, would work.
>
> I want to filter a list of hashes, based on some of the values - (code
> topside)
>
> I have come up with a few variations of the code, with reduce, etc - but
> they all use an anonyous function. The only options I can figure, using
> filter or reduce, require a variable to represent each list element, which
> means an anon-function with a parameter.
>
> Thanks.
>
> Okay, I now have two questions - why does the code-highlighter insist on
> putting the code at the top, instead of in the middle, where I had the
> cursor? :)
>
>
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