Process each N elements of an Array at a time.
Throws InvalidArgument if number of items in arr is not divisible by n.
cb is called as cb(eltI, ..., eltJ) where I is multiple of n and J is I+n-1
Source: stdlib.ngs:1097
arr
Items to iterate in chunks of n
n
Number of items in chunk
cb
Function to be called with values from arr
Returns
arr
Example
[1,2,3,4].each(2, F(a, b) echo("$a - $b")) # Outputs: "1 - 2" and on the next line "3 - 4"