Morse Code
April 28, 2009
Yesterday was the 218th anniversary of the birth of Samuel F. B. Morse, who invented the telegraph. We present this simple exercise in his honor.
Morse Code is an encoding of alphanumeric characters using short and long pulses of sound. Originally developed in the 1840s for the use of Morse’s telegraph, it is still in use today, primarily in the fields of amateur radio and aviation. Letters and digits consist of dots and dashes as shown in the chart at right; a single space is inserted between characters, and an extra space is inserted between words. For instance, “Programming Praxis” is rendered in Morse code as the string “• — — • • — • — — — — — • • — • • — — — — — • • — • — — • • — — • • — • • — — • • — • • • • •“.
| A • — | N — • | 1 • — — — — |
| B — • • • | O — — — | 2 • • — — — |
| C — • — • | P • — — • | 3 • • • — — |
| D — • • | Q — — • — | 4 • • • • — |
| E • | R • — • | 5 • • • • • |
| F • • — • | S • • • | 6 — • • • • |
| G — — • | T — | 7 — — • • • |
| H • • • • | U • • — | 8 — — — • • |
| I • • | V • • • — | 9 — — — — • |
| J • — — — | W • — — | 0 — — — — — |
| K — • — | X — • • — | |
| L • — • • | Y — • — — | |
| M — — | Z — — • • |
Your task is to write functions that convert back and forth between character strings and Morse code. When you are finished, you are welcome to read or run a suggested solution, or to post your solution or discuss the exercise in the comments below.
Programming Praxis 
[…] Praxis – Morse code By Remco Niemeijer Today’s Programming Praxis problem is about morse code. We’re supposed to write a program to convert […]
My Haskell solution. For a version with comments, see http://bonsaicode.wordpress.com/2009/04/28/programming-praxis-morse-code/
import Data.Char import Data.List import Data.List.Split import qualified Data.Map as M plain :: [Char] plain = ['A'..'Z'] ++ ['0'..'9'] morse :: [String] morse = words ".- -... -.-. -.. . ..-. --. .... .. .--- -.- .-.. -- \ \-. --- .--. --.- .-. ... - ..- ...- .-- -..- -.-- --.. \ \.---- ..--- ...-- ....- ..... -.... --... ---.. ----. -----" convert :: Ord a => [a] -> [b] -> a -> b convert from to x = M.fromList (zip from to) M.! x toMorse :: String -> String toMorse = intercalate " " . map (unwords . map (convert plain morse . toUpper)) . words fromMorse :: String -> String fromMorse = unwords . map (map (convert morse plain) . words) . splitOn " " main :: IO () main = do print $ toMorse "Programming Praxis" print $ fromMorse ".--. .-. --- --. .-. .- -- -- .. -. --. \ \.--. .-. .- -..- .. ..."Hm. Evidently this code causes the syntax highlighting plugin to be incredibly slow.
Here is a factor implementation:
I wish I could preview this comment before posting it but here goes:
.NULL { color: #000000; } .COMMENT1 { color: #cc0000; } .COMMENT2 { color: #ff8400; } .COMMENT3 { color: #6600cc; } .COMMENT4 { color: #cc6600; } .DIGIT { color: #ff0000; } .FUNCTION { color: #9966ff; } .INVALID { background: #ffffcc; color: #ff0066; } .KEYWORD1 { color: #006699; font-weight: bold; } .KEYWORD2 { color: #009966; font-weight: bold; } .KEYWORD3 { color: #0099ff; font-weight: bold; } .KEYWORD4 { color: #66ccff; font-weight: bold; } .LABEL { color: #02b902; } .LITERAL1 { color: #ff00cc; } .LITERAL2 { color: #cc00cc; } .LITERAL3 { color: #9900cc; } .LITERAL4 { color: #6600cc; } .MARKUP { color: #0000ff; } .OPERATOR { color: #000000; font-weight: bold; } /home/toups/tinywork/praxis/morse.factorUSING: ascii lists sequences regexp ; : ch>morse ch>upper ( char -- morse-str ) { { CHAR: 0 [ "— — — — —" ] } { CHAR: 1 [ "• — — — —" ] } { CHAR: 2 [ "• • — — —" ] } { CHAR: 3 [ "• • • — —" ] } { CHAR: 4 [ "• • • • —" ] } { CHAR: 5 [ "• • • • •" ] } { CHAR: 6 [ "— • • • •" ] } { CHAR: 7 [ "— — • • •" ] } { CHAR: 8 [ "— — — • •" ] } { CHAR: 9 [ "— — — — •" ] } { CHAR: A [ "• —" ] } { CHAR: B [ "— • • •" ] } { CHAR: C [ "— • — •" ] } { CHAR: D [ "— • •" ] } { CHAR: E [ "• • •" ] } { CHAR: F [ "• • — •" ] } { CHAR: G [ "— — •" ] } { CHAR: H [ "• • • •" ] } { CHAR: I [ "• •" ] } { CHAR: J [ "• — — —" ] } { CHAR: K [ "— • —" ] } { CHAR: L [ "• — • •" ] } { CHAR: M [ "— —" ] } { CHAR: N [ "— •" ] } { CHAR: O [ "— — —" ] } { CHAR: P [ "• — — •" ] } { CHAR: Q [ "— — • —" ] } { CHAR: R [ "• — •" ] } { CHAR: S [ "• • •" ] } { CHAR: T [ "—" ] } { CHAR: U [ "• • —" ] } { CHAR: V [ "• • • —" ] } { CHAR: W [ "• — —" ] } { CHAR: X [ "— • • —" ] } { CHAR: Y [ "— • — —" ] } { CHAR: Z [ "— — • •" ] } [ drop " " ] } case ; : morse>ch ( morse-substring -- char ) { { "— — — — —" [ CHAR: 0 ] } { "• — — — —" [ CHAR: 1 ] } { "• • — — —" [ CHAR: 2 ] } { "• • • — —" [ CHAR: 3 ] } { "• • • • —" [ CHAR: 4 ] } { "• • • • •" [ CHAR: 5 ] } { "— • • • •" [ CHAR: 6 ] } { "— — • • •" [ CHAR: 7 ] } { "— — — • •" [ CHAR: 8 ] } { "— — — — •" [ CHAR: 9 ] } { "• —" [ CHAR: A ] } { "— • • •" [ CHAR: B ] } { "— • — •" [ CHAR: C ] } { "— • •" [ CHAR: D ] } { "• • •" [ CHAR: E ] } { "• • — •" [ CHAR: F ] } { "— — •" [ CHAR: G ] } { "• • • •" [ CHAR: H ] } { "• •" [ CHAR: I ] } { "• — — —" [ CHAR: J ] } { "— • —" [ CHAR: K ] } { "• — • •" [ CHAR: L ] } { "— —" [ CHAR: M ] } { "— •" [ CHAR: N ] } { "— — —" [ CHAR: O ] } { "• — — •" [ CHAR: P ] } { "— — • —" [ CHAR: Q ] } { "• — •" [ CHAR: R ] } { "• • •" [ CHAR: S ] } { "—" [ CHAR: T ] } { "• • —" [ CHAR: U ] } { "• • • —" [ CHAR: V ] } { "• — —" [ CHAR: W ] } { "— • • —" [ CHAR: X ] } { "— • — —" [ CHAR: Y ] } { "— — • •" [ CHAR: Z ] } [ drop 32 ] } case ; : string>morse ( string -- morse-string ) sequence>cons { } [ ch>morse suffix ] foldl " " join ; : morse>string ( morse-string -- string ) R/ [ ]{2,}/ re-split [ >string morse>ch ] map >string ;python
from string import lowercase, digits morse = dict((c, (""".- -... -.-. -.. . ..-. --. .... .. .--- -.- .-.. -- -. --- .--. --.- .-. ... - ..- ...- .-- -..- -.-- --.. ----- .---- ..--- ...-- ....- ..... -.... --... ---.. ----.""".split() + [" "])[i]) for i, c in enumerate(lowercase + digits + " ")) def to_morse(text): return "".join([morse[c] + " " for c in text if c in morse])Hand to apply, gravity The same?Amounts of website, for that.That brings with, by -. for structural Seattle SEO, results for optimizing the cheapest option.Limit Holdem is, ways a great.,
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ruby solution (http://codepad.org/T2cG3fe1)
class String MORSE_CODE = [ ['a', '.-'], ['b', '-...'], ['c', '-.-.'], ['d', '-..'], ['e', '.'], ['f', '..-.'], ['g', '--.'], ['h', '....'], ['i', '..'], ['j', '.---'], ['k', '-.-'], ['l', '.-..'], ['m', '--'], ['n', '-.'], ['o', '---'], ['p', '.--.'], ['q', '--.-'], ['r', '.-.'], ['s', '...'], ['t', '-'], ['u', '..-'], ['v', '...-'], ['w', '.--'], ['x', '-..-'], ['y', '-.--'], ['z', '--..'], ['1', '.----'], ['2', '..---'], ['3', '...--'], ['4', '....-'], ['5', '.....'], ['6', '-....'], ['7', '--...'], ['8', '---..'], ['9', '----.'], ['0', '-----'], ] def to_morse self.split(' ').collect { |word| _to_morse word }.join ' ' end def to_ascii self.split(' ').collect { |word| _to_ascii word }.join ' ' end private def _to_morse string string.downcase.split(//).collect do |letter| MORSE_CODE.select { |pair| pair[0].eql? letter } end.map { |pair| pair[0][1] }.join(' ') end def _to_ascii string string.downcase.split(' ').collect do |code| MORSE_CODE.select { |pair| pair[1].eql? code } end.map { |pair| pair[0][0] }.join end end message = 'Programming Praxis' puts message.to_morse puts message.to_morse.to_ascii