Fix/contrast but with equality check on different pattern

Questions and Answers
1

The function fix conditionally applies a function to a pattern, eg fix f e p applies function f to any events in pattern p that match those in pattern e (I think).

Is there a version of this that compares e to a pattern other than p, eg a function fixWhen f e q p that applies f to events in p whenever events in e match those in q? Or can this be composed from existing functions?

I have been looking at how to get patterns to interact with each other (like here) and thought a function like this might be a good general-purpose way to do it? For example something like this would silence the arpy whenever the snare sounds:

let p1 = s "~ sn ~ sn"
let p2 = n "0 1 2 3 4 5 6" # sound "arpy"
d1 $ stack [
    p1,
    fixWhen (# silence) (s "sn") p1 $ p2
]

If this doesn't exist, does it seem feasible to write it? (Been a few years since I wrote any Haskell). Or is there a better way to do this with existing functions?

2 Likes
2

This is an interesting question but unfortunately I'm not versed enough in Tidal innards and Haskell to answer it completely.
Looking at the source code of contrast, I see that it is a particularization (?) of contrastBy, which does not test for equality but rather uses an arbitrary boolean function. Maybe by feeding it a carefully crafted function you could get it to test on another pattern?