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Phone number coding program in Clojure
;; Adapted from "An empirical comparison of C, C++, Java, Perl,
;; Python, Rexx, and Tcl for a search/string-processing program"
;; by Lutz Prechelt
;; This was a 15-minute effort while listening to a talk. It's *not*
;; well thought-out or designed.
;; By Stuart Sierra,
;; @stuartsierra on Twitter
(ns phone-code
(:require [clojure.set :as set]))
(def words
(string/split-lines (slurp "/usr/share/dict/words")))
(def mnemonics {\2 "ABC"
\3 "DEF"
\4 "GHI"
\5 "JKL"
\6 "MNO"
\7 "PQRS"
\8 "TUV"
\9 "WXYZ"})
(def char-code
(into {} (for [[digit string] mnemonics
letter string]
[letter digit])))
(defn word-code [word]
(map char-code (.toUpperCase word)))
(def words-for-num
(group-by word-code (filter #(<= (count %) 7) words)))
(defn encode
"Given phone number digits as a string, return a set of possible
word phrases which can be made from it."
[number]
(reduce clojure.set/union
(for [split-point (range (count number))]
(let [[first-words second-words] (map words-for-num (split-at split-point number))]
(if (seq first-words)
(set (for [first-word first-words
second-word second-words]
(str first-word " " second-word)))
(set second-words))))))
(comment
;; The first letter-code phone number, during a measles epidemic,
;; was 1-800-MEASLES.
(encode "6327537")
;;=> #{... "measles" ... }
)
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