CODEWITHSUNDEEP
haskell
Titania Lo
Titania Lo

Reputation: 65

Terminal and putStrLn output difference

Whe I type out into terminal the code below, it can successfully display all the detail I need.

avg "Vivo" testDatabase

But when I try to show that it works with the code below, it gives me an error - It couldn't match type 'Float' with '[Char]'. How should I try to fix this error?

--the function for code
avg :: String -> [Spa] -> Float
avg avgAreaRating spas = fromIntegral (sum lvlrating) /  fromIntegral (length lvlrating)
  where area = spaArea avgAreaRating spas
        lvlrating = concatMap getLevelRating area 

--code
show 5  = putStrLn $ avg "Vivo" testDatabase

Upvotes: 2

Views: 91

Answers (1)

Robin Zigmond
Robin Zigmond

Reputation: 18249

putStrLn needs a String as its argument. Your error occurs because you are calling it on a Float - if the types don't match, your code won't compile.

The reason it works when you just put avg "Vivo" testDatabase into GHCi is that GHCi automatically and implicitly calls print on anything you pass to it. Unlike putStrLn, print can take as argument any type which can be converted to a string (via the Show typeclass - which always includes Float).

So all you need to do is replace putStrLn with print:

print $ avg "Vivo" testDatabase

Upvotes: 4

Related Questions