A-M baby

Task/Morse-code/Haskell/morse-code-3.hs

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+module MorsePlaySox (play) where
+
+import Sound.Sox.Play
+import Sound.Sox.Option.Format
+import Sound.Sox.Signal.List
+import Data.Int
+import System.Exit
+import MorseCode
+
+samps = 15           -- samples/cycle
+freq  = 700          -- cycles/second (frequency)
+rate  = samps * freq -- samples/second (sampling rate)
+
+type Samples = [Int16]
+
+-- One cycle of silence and a sine wave.
+mute, sine :: Samples
+mute = replicate samps 0
+sine = let n = fromIntegral samps
+           f k = 8000.0 * sin (2*pi*k/n)
+       in map (round . f . fromIntegral) [0..samps-1]
+
+-- Repeat samples until we have the specified duration in seconds.
+rep :: Float -> Samples -> Samples
+rep dur = take n . cycle
+    where n = round (dur * fromIntegral rate)
+
+-- Convert Morse symbols to samples.  Durations are in seconds, based on
+-- http://en.wikipedia.org/wiki/Morse_code#Representation.2C_timing_and_speeds.
+toSamples :: MSym -> Samples
+toSamples Dot  = rep 0.1 sine
+toSamples Dash = rep 0.3 sine
+toSamples SGap = rep 0.1 mute
+toSamples CGap = rep 0.3 mute
+toSamples WGap = rep 0.7 mute
+
+-- Interpret the stream of Morse symbols as sound.
+play :: Morse -> IO ExitCode
+play = simple put none rate . concatMap toSamples