Hello Steafan, On Wed, Aug 15, 2018 at 09:06:40PM +0000, Stefan Chacko wrote:
1. What is the use of making definitions compared to having no definitions? Is it just like a comment for documation or does it really make a difference in compiling the code?
Writing signatures is always useful: - to prototype (and let the compiler complain about wrong types) - to restrict a function to some types only, e.g. intHead :: [Int] -> Int intHead is = head is - to have an immediate, clear, verifiable documentation near the functions
2. What does the arrow(->) mean in such a definition? [...] For example there is sumWithL :: [Int] -> Int -> Int
`[Int] -> Int -> Int` can be (with great approximation) be read "this function takes two arguments, `[Int]` and `Int`, to return an `Int`. More precisely, if you provide `[Int]` you'll get back a function that takes an Int to return one Int (Int -> Int), and if you (finally) pass an Int to that, you receive the final result.
1. Why do we use clinches in such definitions. I concluded you need clinches if a function is not associative
(->) (called `function application`) associates to the right, so sumWithL :: [Int] -> Int -> Int is equal to sumWithL :: [Int] -> (Int -> Int) If you want a function that takes a function `[Int] -> Int` to return an Int you got to put parentheses: sumWithL :: ([Int] -> Int) -> Int Hope it was clear! -F p.s. haskell@haskell.org is for announcements only, so I am removing it from cc.