CODEWITHSUNDEEP
haskellmathmodule
Heligo
Heligo

Reputation: 165

How do you write the mathematical |x| in haskell?

How do you get the (x - y) < 20 always positive?

I'd like to make a condition for:

getJOL :: [Int] -> String
getJOL [w,x,y,z] = if x - w < 20 && y - x < 20 && z - y < 20
                     then "Good calibration"
                     else "Bad calibration"

The difference between two values must be positive.

Upvotes: 3

Views: 772

Answers (2)

leftaroundabout
leftaroundabout

Reputation: 120741

Yes, abs is the function you want. That's the conventional name for |x| in most languages.

BTW you should probably not hard-code the case for exactly four list-elements. It's both unsafe (what if someone hands you a list with five elements?) and repetitive. Just recurse over the list, and abort when a pair with too large distance is found:

getJOL (w:x:ys)
  | abs (x - w) >= 20  = "Bad calibration"
getJOL (_:xs) = getJOL xs
getJOL [] = "Good calibration"

Upvotes: 10

Jones1220
Jones1220

Reputation: 786

Just use the absolute values abs. This will check, whether the absolute difference is lower than 20.

getJOL :: [Int] -> String
getJOL [w,x,y,z] = if abs(x - w) < 20 && abs(y - x) < 20 && abs(z - y) < 20
                     then "Good calibration"
                     else "Bad calibration"

Upvotes: 5

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