-- Some examples demonstrating recursion and pattern matching.
-- by Scot Drysdale on 9/27/07, modified 9/25/2008

-- Computes the length of a string
strLength         :: [Char] -> Int
strLength []       = 0
strLength (c:rest) = 1 + strLength rest

-- listSum implemented recursively (from SOE)
listSum           :: [Double] -> Double
listSum []         = 0.0
listSum (num:rest) = num + listSum rest

-- Reverses a string
reverseString  ::  [Char] -> [Char]
reverseString []     = []
reverseString (x:xs) = reverseString xs ++ [x]

-- A faster way to reverse a string, using a helper function
reverseStringFast  ::  [Char] -> [Char]
reverseStringFast xs = rev [] xs
   where rev acc []     = acc
         rev acc (x:xs) = rev (x:acc) xs