Clojure practice - 2

After finishing the previous post I noticed that Kaloz's solution was a bit more concise, not leaning on a helper function. So here is a "more compact" version, even puttin the number->characters mapping definition in the same expression.

(defn compact-combinations [number]
  (let [num->chars { \2  "ABC" \3  "DEF" \4  "GHI" \5  "JKL" 
                    \6  "MNO" \7  "PQRS" \8  "TUV" \9  "WXYZ"}
        red-fn (fn [acc d]
                 (m/match (num->chars d)
                   nil acc
                   chs (for [c chs
                             i acc]
                           (str i c))))] 
    (reduce red-fn [""] number)))

(println (compact-combinations "34"))

or, purely for the sake of example, having even the println in it

(let [combinations (fn [number] 
                     (let [num->chars {\2  "ABC" \3  "DEF" \4  "GHI" \5  "JKL" 
                                       \6  "MNO" \7  "PQRS" \8  "TUV" \9  "WXYZ"}
                           red-fn (fn [acc d]
                                    (m/match (num->chars d)
                                      nil acc
                                      chs (for [c chs
                                                i acc]
                                              (str i c))))] 
                       (reduce red-fn [""] number)))]
  (println (combinations "514")))

Clojure practice

Recently I have dabbled into Clojure. I've been planning a post for a while, but since now Kaloz has posted a Scala functional programming demonstration, the time has come to reply in kind. Please, read his post to get the problem, here I take the lazy way and simply show a Clojure solution.

(ns clojure-study.garbage
  (:require [clojure.core.match :as m]))

(def num->chars { 
                  \2  "ABC"
                  \3  "DEF"
                  \4  "GHI"
                  \5  "JKL"
                  \6  "MNO"
                  \7  "PQRS"
                  \8  "TUV"
                  \9  "WXYZ"})

(defn- red-fn [resolvedStrings number]
  (m/match (num->chars number)
    nil resolvedStrings
    item (for [c item
               i resolvedStrings]
            (str i c))))

(defn combinations [number]
  (reduce red-fn [""] number))

(println (combinations "77501998489"))

DDD reference project

I haven't posted in a while, but wasn't completely idle. I'd like to improve our way of doing DDD in the team I'm working in, so I have endeavoured to create a reference DDD project, where good practices, distilled experiences and some new ideas are demonstrated. The result is here, general explanatory notes on the wiki. It was quite a task, but a rewarding one.