While trying to code the Clapping Music piece from Steve Reich I noticed that Mercury actually lacks some method/function/way to allow creating a list iteratively.

The result of the code is currently this:

// the initial rhythm, played 8 times
list ptn copy([1 1 1 0 1 1 0 1 0 1 1 0] 8)

// the repetitions with shifts for every step
list ptn2 join(ptn rot(ptn -1) rot(ptn -2) rot(ptn -3) rot(ptn -4) rot(ptn -5) rot(ptn -6) rot(ptn -7) rot(ptn -8) rot(ptn -9) rot(ptn -10) rot(ptn -11))

It is clear there is lots of repetition needed in order to be able to rotate the pattern after every 8 duplicates. It would be interesting to see if there is a way to do this without the repetition of the code. For example providing a list on a function argument that would usually only accept a single number could make that function perform it multiple times:

list ptn copy([1 1 1 0 1 1 0 1 0 1 1 0] 8)

list ptn2 join(ptn rot(ptn [-1 -2 -3 -4 -5 -6 -7 -8 -9 -10 -11]))

This could be written even shorter, by using the spreadInc() method:

list ptn copy([1 1 1 0 1 1 0 1 0 1 1 0] 8)

list ptn2 rot(ptn spreadInc(12 0 -11))

Another option is that there is some kind of for() or iterate()/iter() method, that performance a function iteratively by putting the value from another list as argument. For example:

list ptn copy([1 1 1 0 1 1 0 1 0 1 1 0] 8)

// performance the function rot() multiple times for every value of the first list
// using i as a placeholder for the value from that list
list ptn2 iter([0 -1 -2 -3 ... -11] rot(ptn i)) 

The current result of coding the Clapping Music:

https://mercury-playground.pages.dev/#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