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 2 3 4 5
1 3 5 7 9

 5+':1 2 3 4 5
6 3 5 7 9