Hi there.

I'm trying to write a simple program in Haskell that can determine someone's body mass index.

Here's what I have written:

type Height = Float

type Weight = Float

type PeopleStats = [(String, Height, Weight)]

and...

bmi :: Height -> Weight -> Float

bmi heightCm weightKg = weightKg/(heightCm)^2

healthy :: Height -> Weight -> Bool

healthy heightCm weightKg

| 25 > index && 18 < index = True

| otherwise = False

where index = bmi heightCm weightKg

So far, the function "healthy" can calculate someone's BMI, and the function "healthyPeople" returns a boolean statement determining if the person's BMI falls within the limits which is considered normal for a healthy person.

I want to write a function called "healthyPeople".

healthyPeople :: PeopleStats -> [String]

This function needs to take a list of PeopleStats and returns a list of names (Strings) of people who are deemed to be "healthy" from the "healthy" function.

For example:

If I input [("Lee", 65, 185), ("Wang", 170, 100), ("Tsu", 160, 120)] I will get a list of the names of the people whose BMI returns true form the boolean function in "healthy".

Please help !!!!