each prior

Each prior

f':x
x f':y

Each prior applies a two argument function(dyad) to each element, and the element prior to it.

If provided with a left argument, uses it as an initial value.

 -':1 6 2 3 4
1 5 -4 1 1

 5-':1 6 2 3 4
-4 5 -4 1 1