Here's one way you could do part of it:
https://gist.github.com/johnwalker/7fcf1f988cd5e6e21fd5
(let [day->index (into {} (map-indexed (fn [k v] [v k]) "MTWRFSN"))
;; So M (Monday) maps to 0, S (Saturday) maps to 5
initial-state (into [] (repeat 7 0))]
;; Create an empty vector of seven zeroes
(reduce (fn [x i] (assoc x i 1)) initial-state (map day->index "MWF")))
;; Map each day to an index.
;; (day->index \M) is 0
;; so (map day->index "MWF)
;; is (0 2 4)
;; But we want [1 0 1 0 1 0 0]
;; So start with the seven zeroes, and add 1s for each date
I know what you mean by "You could have just used (map ...)". It helps me
when I think about the number of elements I want (versus what I started
with), and how independent elements are from one another.
On Monday, September 22, 2014 11:45:23 AM UTC-7, J David Eisenberg wrote:
>
> As part of a larger program, I'm testing a function that will turn a
> string of days on which a class occurs (such as "MWF") into a list of seven
> numbers: (1 0 1 0 1 0 0).
> I first translate"TH" (Thursday) to "R" and "SU" (Sunday) to "N" to make
> things a bit easier.
>
> I came up with the following code:
>
> (defn days-number-maker
> "Recursively compare first item in days of week with
> first item in string of days. If matching, add a 1,
> else add a zero to the result"
> [all-days day-string result]
> (if (empty? all-days) (reverse result)
> (if (= (first all-days) (first day-string))
> (recur (rest all-days)(rest day-string) (conj result 1))
> (recur (rest all-days) day-string (conj result 0)))))
>
> (defn days-to-numbers
> "Change string like MTTH to (1 1 0 1 0 0 0)"
> [day-string]
> (let [days (clojure.string/replace
> (clojure.string/replace day-string #"TH" "R") #"SU" "N")]
> (days-number-maker "MTWRFSN" days (list))))
>
> The good news: the code works. The bad news: I'm convinced I'm doing it
> wrong, in the moral purity sense of the word. Something inside of me says,
> "You could have just used (map...) to do this the *right* way," but I can't
> see how to do it with (map). So, my two questions are:
>
> 1) Is there such a thing as "the Clojure way," and if so,
> 2) How can I rewrite the code to be more Clojure-ish?
>
>
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