TidalCycles when and whenmod apply transforms based on a predicate or modular arithmetic test on the cycle number

when test f p applies f to pattern p only when the test function returns True for the current cycle number. The test is any Haskell function Int -> Bool, giving full flexibility: when ((elem '4').show) transforms on any cycle whose number contains the digit 4 (cycle 4, 14, 24, 34, 40…). whenmod m n f p tests whether currentCycle mod m >= n: whenmod 8 4 (fast 2) doubles speed on cycles 4,5,6,7, then 12,13,14,15, etc. This is effectively ‘every other block of m cycles, start the transform at position n.’ ifp extends this to two-branch if-else: apply f1 when True, f2 when False.

Examples

d1 $ when ((elem '4').show) (striate 4) $ sound "hh hc"
d1 $ whenmod 8 4 (fast 2) (sound "bd sn kurt")
d1 $ ifp ((== 0).(flip mod 2)) (striate 4) (# coarse "24 48") $ sound "hh hc"

Assessment

Describe the cycle-number pattern on which whenmod 6 3 (rev) applies its transformation. Write a when expression that doubles speed only on prime-numbered cycles. When would ifp be more useful than two separate when expressions?