slice extracts some consecutive elements from within a list.
slice(list, startindex, endindex)
startindex is inclusive, while
endindex is exclusive. This function returns
an error if either index is outside the bounds of valid indices for the given
> slice(["a", "b", "c", "d"], 1, 3)[ "b", "c",]
substrperforms a similar function for characters in a string, although it uses a length instead of an end index.