cannot parse arpeggiator pattern "up&down"

[jwaldmann]

copied from https://club.tidalcycles.org/t/arpeggiator-patterns-up-down-down-up/3689

tidal> d1 $ n (arp "up&down" "c'maj7") # s "superpiano"
Error in pattern: Syntax error in sequence:
  "up&down"
     ^  
unexpected '&'
expecting charnum, rest, "[", "{", "<", "^", ".", "?" or end of input

looks like a bug to me, as the reference doc suggests that it should work http://tidalcycles.org/docs/patternlib/tour/harmony_melody/#arp

I don't have a fix, need to look up details of the mini-notation parser.

---

While we're at it, the implementation https://github.com/tidalcycles/Tidal/blob/main/src/Sound/Tidal/UI.hs#L1429 could be improved a bit

• replace list (arps) by some map type that has more efficient lookup
• float it out of function _arp, to top level (else, the list might get built each time the function is used)

On the other hand, don't fix it if it ain't broken - the above points are probably not critical for performance. (strings as keys are bad in any case, and this can't be easily changed in Tidal)

[jwaldmann]

Note that this works (with pure)

Prelude Sound.Tidal.Context> n (arp (pure "up&down") "c'maj7") # s "superpiano"
(0>⅛)|n: Note {unNote = 0.0}n, s: "superpiano"
(⅛>¼)|n: Note {unNote = 4.0}n, s: "superpiano"
(¼>⅜)|n: Note {unNote = 7.0}n, s: "superpiano"
...

mini notation parser won't accept & since

    415 pString :: MyParser String
    416 pString = do c <- pCharNum <?> "charnum"
    417              cs <- many (letter <|> oneOf "0123456789:.-_") <?> "string"
    418              return (c:cs)

Should & be added to the list of extra characters here?