Finding the number of roots in a quadratic equation in haskell

rootFunction :: Float -> Float -> Float -> Int

rootFunction a b c

| a == 0        = dRoots a b c

| otherwise     = numberNDroots a b c

numberNDroots :: Float -> Float -> Float -> Int

numberNDroots a b c 

| b^2 > (4.0*a*c)      = 2

| b^2 == (4.0*a*c)     = 1

| b^2 < (4.0*a*c)      = 0

dRoots :: Float -> Float -> Float -> Int

dRoots a b c 

| b /= 0               = 1

| b == 0 && c /= 0     = 0

| b == 0 && c == 0     = 3