sqrt.hs

--fuinction to get the square of an integer
square::Int->Int
square a = a*a


--function to find the mid of two integers floor to ,lower if fractional
mid::Int->Int->Int
mid a b = (a+b) `div` 2


--function to find the root given one arguement
root::Int->Int
root a=root a 0 a where
        root a lowerLimit upperLimit
                | square(mid lowerLimit upperLimit)==a = mid  lowerLimit upperLimit
                | lowerLimit == upperLimit  = if square(lowerLimit)<a then a else lowerLimit-1
                | square(mid lowerLimit upperLimit)>a = root a lowerLimit (mid lowerLimit upperLimit - 1)
                | square(mid lowerLimit upperLimit)<a = root a (mid lowerLimit upperLimit + 1) upperLimit

main = do
        input <- getLine
        print (root (read input))

Program to find the square root in log n complexity in #haskell
prints the nearest integer less than or equal to the square root of the number given