Description
Given a base num and a limit, write a function largestPower that returns the largest power of num (i.e., num k where k≥0) that is less than or equal to the limit.
largestPower:: Int -> Int -> Integer
largestPower num limit
| (num == 1 || num == 0) = num
| num > limit = -1
| otherwise = findPower num 1 limit
findPower num cur limit
| cur > limit = cur `div` num
| otherwise = findPower num (cur*num) limit
largestPower' b n = last [b^x | x [0..], b^x <= n]