(surprising/inconsistent) handling of begin/end attributes in slice

Questions and Answers
1

(there was a recent question about speed with splice, this is about begin and end with slice)

This is fine (selected part of sample gets cut in half):

ghci> chop 2 $ s "led" # begin 0.03 # end 0.86
(0>½)|begin: 3.0e-2f, end: 0.44499999999999995f, s: "led"
(½>1)|begin: 0.44499999999999995f, end: 0.86f, s: "led"

but this is surprising (does not cut the sample):

ghci> slice 2 0 $ s "led" # begin 0.03 # end 0.86
(0>1)|begin: 3.0e-2f, end: 0.86f, s: "led"

this only works when no begin/end are given:

ghci> slice 2 0 $ s "led" 
(0>1)|begin: 0.0f, end: 0.5f, s: "led"

To add to the confusion, function _slice does ignore begin/end:

ghci> _slice 2 0 $ s "led" # begin 0.03 # end 0.86
(0>1)|begin: 0.0f, end: 0.5f, s: "led"

Implementation of slice (https://hackage.haskell.org/package/tidal-1.9.4/docs/src/Sound.Tidal.Control.html#slice) has

slice pN pI p = P.begin b # P.end e # p where ...

so if p does have begin/end, then these take precedence, by the semantics of #.

Implementation of _slice (https://hackage.haskell.org/package/tidal-1.9.4/docs/src/Sound.Tidal.Control.html#_slice) has this

_slice n i p =  p  # P.begin ... # P.end ...

and this will ineed ignore begin/end attributes in p.

Implementation of chop (https://hackage.haskell.org/package/tidal-1.9.4/docs/src/Sound.Tidal.Control.html#chop) contains some local magic (chomp) for begin/end computations.

Shouldn't chomp be applied in slice as well?

NB: I found the "led" sample tricky to handle, but finally came up with this:

let frev n = rev . fast n . rev . slow n
in  d1
  $ (segment 2 $ fmap (2^) $ 0.1 ~> irand 4) >>= \ j -> 
      slow (segment 2 $ fmap (2^) $ 0.2 ~> irand 3)
    $ frev (pure j)
    $ chop 32
     (s "led" # begin 0.03 # end 0.86 # speed 0.96 # pan rand)
   * speed (segment 2 $ fmap (2^) $ 0.3 ~> irand 2)
   # delay 1 # delayfb (choose [0,0.5]) # delayt (120/135/4 )
   # room 1 # size 0.8

(the hard part was to figure out numerical values 0.03, 0.86, 0.96)

[EDIT] rendered audio: tidal/code/led.ogg · master · waldmann / computer-mu · GitLab

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