code ← ##.morse text            ⍝ Conversion to/from Morse code.
text ← ##.morse code            ⍝ Samuel Morse 1791-1872.

Given  a text vector of characters from:  "A-Z", "0-9", ".,:?'-/()"@= ", [morse]
returns a nested vector of the equivalent Morse codes.

Conversely, given a nested vector of Morse codes, the function returns the equi-
valent plain text.

Unrecognised  characters  and codes are ignored.  In particular, [morse] ignores
lower-case letters "a-z".

Morse alphabet tree
-------------------
Morse  chooses shorter codes for more frequently occurring letters (in English).
The  designers  of  old-style linotype type-setting machines judged the order of
this frequency to be: ETAOIN SHRDLU CMFWYP VBGKQJ XZ.

                  .               │               _
                  ┌───────────────┴───────────────┐
           .      E       _               .       T       _
          ┌───────┴───────┐               ┌───────┴───────┐
      .   I   _       .   A   _       .   N   _       .   M   _
      ┌───┴───┐       ┌───┴───┐       ┌───┴───┐       ┌───┴───┐
    . S _   . U     . R     . W _   . D _   . K _   . G _     O
    ┌─┴─┐   ┌─┘     ┌─┘     ┌─┴─┐   ┌─┴─┐   ┌─┴─┐   ┌─┴─┐
    H   V   F       L       P   J   B   X   C   Y   Z   Q

Ref: http://en.wikipedia.org/wiki/Morse_code

(muse:

    It  is  said  that  experienced  telegraph operators, who used morse code to
    transmit messages, could recognise each others tapping style; the equivalent
    of being able to distinguish someone's handwriting (or coding style).
)

Examples:

    disp morse 'HELLO WORLD'                    ⍝ Morse code from plain text.
┌→───┬─┬────┬────┬───┬─┬───┬───┬───┬────┬───┐
│....│.│.-..│.-..│---│/│.--│---│.-.│.-..│-..│
└───→┴→┴───→┴───→┴──→┴→┴──→┴──→┴──→┴───→┴──→┘

    morse morse'ROUND TRIP'                     ⍝ ... and back again.
ROUND TRIP

    disp morse 'Samuel Finley Breese'           ⍝ lower-case letters ignored,
┌→──┬─┬────┬─┬────┐
│...│/│..-.│/│-...│
└──→┴→┴───→┴→┴───→┘

    disp morse ucase 'Samuel Finley Breese'     ⍝  ... so convert to upper-case.
┌→──┬──┬──┬───┬─┬────┬─┬────┬──┬──┬────┬─┬────┬─┬────┬───┬─┬─┬───┬─┐
│...│.-│--│..-│.│.-..│/│..-.│..│-.│.-..│.│-.--│/│-...│.-.│.│.│...│.│
└──→┴─→┴─→┴──→┴→┴───→┴→┴───→┴─→┴─→┴───→┴→┴───→┴→┴───→┴──→┴→┴→┴──→┴→┘

See also: ucase packH

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