Programming Praxis

6 Responses to “1-800-PPRAXIS”

1. Globules said

   September 19, 2018 at 2:39 AM

   Here’s a Haskell version. We keep any non-letters.

   import           Data.Char (toUpper)
   import qualified Data.Map.Strict as M
   import           Data.Maybe (fromMaybe)
   
   letterMap :: M.Map Char Char
   letterMap = M.fromList $ concatMap (\(cs, d) -> map (\c -> (c, d)) cs) letsDig
     where letsDig = [("ABC", '2'), ("DEF",  '3'), ("GHI", '4'), ("JKL",  '5'),
                      ("MNO", '6'), ("PQRS", '7'), ("TUV", '8'), ("WXYZ", '9')]
   
   unPhoneword :: String -> String
   unPhoneword = map (\c -> fromMaybe c (M.lookup (toUpper c) letterMap))
   
   test :: String -> IO ()
   test pw = putStrLn $ pw ++ " -> " ++ unPhoneword pw
   
   main :: IO ()
   main = do
     test "1-800-PPRAXIS"
     
     -- These are from https://en.wikipedia.org/wiki/Phoneword.
     test "+1-514-AUTOBUS"
     test "13TAXI"
     test "1800-THRIFTY"
     test "1-US-RENT-A-WRECK"
   

   $ ./unphoneword
   1-800-PPRAXIS -> 1-800-7772947
   +1-514-AUTOBUS -> +1-514-2886287
   13TAXI -> 138294
   1800-THRIFTY -> 1800-8474389
   1-US-RENT-A-WRECK -> 1-87-7368-2-97325
   
2. Alex B said

   September 19, 2018 at 2:47 AM

   Python version. As with Globules, I kept any non-letters.

   import string
   
   def telemapper(phone_num):
       src = string.ascii_uppercase
       tgt = '22233344455566677778889999'
       mapping = dict(zip(src, tgt))
       phone_num = phone_num.upper()
   
       return ''.join(mapping[c] if c in src else c for c in phone_num)
   

   Outputs as follows:

   >>> telemapper('1-800-PPRAXIS')
   '1-800-7772947'
   >>> telemapper('1-800-ppraxis')
   '1-800-7772947'
   >>> telemapper('+1-514-AUTOBUS')
   '+1-514-2886287'
   >>> telemapper('1-US-RENT-A-WRECK')
   '1-87-7368-2-97325'
   >>> telemapper('1-888-Wait-Wait')
   '1-888-9248-9248'
   >>> 
   
3. Daniel said

   September 19, 2018 at 4:43 AM

   Here’s a solution in C.

   #include <stdio.h>
   #include <stdlib.h>
   
   int main(int argc, char* argv[]) {
       if (argc != 2) {
           fprintf(stderr, "Usage: %s <PHONE_NUMBER>\n", argv[0]);
           return EXIT_FAILURE;
       }
       for (int i = 0;; ++i) {
           char c = argv[1][i];
           if (c == '\0') break;
           if (c >= 'A' && c <= 'Z') c += 'a' - 'A';
           static char lookup[] = "22233344455566677778889999";
           if (c >= 'a' && c <= 'z') c = lookup[c - 'a'];
           printf("%c", c);
       }
       printf("\n");
       return EXIT_SUCCESS;
   }
   

   Example:

   $ ./a.out 1-800-PPRAXIS
   1-800-7772947
   
4. Daniel said

   September 19, 2018 at 5:00 AM

   Here’s a code golf solution in Python.

   from string import ascii_letters as l
   
   def convert(s):
       return "".join("22233344455566677778889999"[l.index(c) % 26] if c in l else c for c in s)
   
   s = "1-800-PPRAXIS"
   print(convert(s))
   

   Output:

   1-800-7772947
   
5. V said

   September 20, 2018 at 12:12 PM

   Solution in ruby.

   
   # Simple obvious solution: direct key/value mapping using a hash.
   def translate(text)
     text.chars.map do |c|
       { 
         a: 2, b: 2, c: 2,
         d: 3, e: 3, f: 3,
         g: 4, h: 4, i: 4,
         j: 5, k: 5, l: 5,
         m: 6, n: 6, o: 6,
         p: 7, q: 7, r: 7, s: 7,
         t: 8, u: 8, v: 8,
         w: 9, x: 9, y: 9, z: 9
       }[c.downcase.to_sym] or c
     end.join
   end
   
   # Still mapping key to values using a hash.
   # This time the keys contains all letters of a number.
   def translate(text)
     text.chars.map do |c|
       match = {
         "abc"  => 2,
         "def"  => 3,
         "ghi"  => 4,
         "jkl"  => 5,
         "mno"  => 6,
         "pqrs" => 7,
         "tuv"  => 8,
         "wxyz" => 9
       }.detect { |k,v| k.include?(c.downcase) }
       
       match ? match.last : c
     end.join
   end
   
   # And this one does the mapping with an array infering the value from the index.
   def translate(text)
     mapping = ["abc", "def", "ghi", "jkl", "mno", "pqrs", "tuv", "wxyz"]
     text.chars.map do |c|
       match = mapping.find_index { |s| s.include?(c.downcase) }
       match ? (match + 2) : c
     end.join
   end
   
   def test_translate(input, target)
     output = translate(input)
     puts
     puts "input: #{input}"
     puts "output: #{output}"
     puts "pass: #{output == target ? '✅' : '❌'}"
   end
   
   test_translate "1-800-PPRAXIS", "1-800-7772947"
   test_translate "+1-514-AUTOBUS", "+1-514-2886287"
   test_translate "13TAXI", "138294"
   test_translate "1800-THRIFTY", "1800-8474389"
   test_translate "1-US-RENT-A-WRECK", "1-87-7368-2-97325"
   
   

   All three version output:

   input: 1-800-PPRAXIS
   output: 1-800-7772947
   pass: ✅

   input: +1-514-AUTOBUS
   output: +1-514-2886287
   pass: ✅

   input: 13TAXI
   output: 138294
   pass: ✅

   input: 1800-THRIFTY
   output: 1800-8474389
   pass: ✅

   input: 1-US-RENT-A-WRECK
   output: 1-87-7368-2-97325
   pass: ✅

   Tests from @Globules
6. Tim McNamara 🐍🦀 (@timClicks) said

   October 5, 2018 at 2:19 AM

   A small improvement to Alex B’s solution is to make use of the Python dict’s ability to return a default when it can’t find a key:

   import string
    
   def telemapper(phone_num):
       src = string.ascii_uppercase
       tgt = '22233344455566677778889999'
       mapping = dict(zip(src, tgt))
    
       return ''.join(mapping.get(c, c) for c in phone_num.upper())
   

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