diff options
Diffstat (limited to 'haskell.html.markdown')
| -rw-r--r-- | haskell.html.markdown | 23 |
1 files changed, 12 insertions, 11 deletions
diff --git a/haskell.html.markdown b/haskell.html.markdown index f28fcfe7..34eee748 100644 --- a/haskell.html.markdown +++ b/haskell.html.markdown @@ -81,7 +81,7 @@ not False -- True [5,4..1] -- [5, 4, 3, 2, 1] -- indexing into a list -[0..] !! 5 -- 5 +[1..10] !! 3 -- 4 -- You can also have infinite lists in Haskell! [1..] -- a list of all the natural numbers @@ -195,11 +195,11 @@ foo 5 -- 15 -- function composition -- the (.) function chains functions together. -- For example, here foo is a function that takes a value. It adds 10 to it, --- multiplies the result of that by 5, and then returns the final value. -foo = (*5) . (+10) +-- multiplies the result of that by 4, and then returns the final value. +foo = (*4) . (+10) --- (5 + 10) * 5 = 75 -foo 5 -- 75 +-- (5 + 10) * 4 = 60 +foo 5 -- 60 -- fixing precedence -- Haskell has another operator called `$`. This operator applies a function @@ -209,14 +209,15 @@ foo 5 -- 75 -- the expression on its right is applied as the parameter to the function on its left. -- before -(even (fib 7)) -- false - --- after -even . fib $ 7 -- false +even (fib 7) -- false -- equivalently even $ fib 7 -- false +-- composing functions +even . fib $ 7 -- false + + ---------------------------------------------------- -- 5. Type signatures ---------------------------------------------------- @@ -282,7 +283,7 @@ foldl (\x y -> 2*x + y) 4 [1,2,3] -- 43 foldr (\x y -> 2*x + y) 4 [1,2,3] -- 16 -- This is now the same as -(2 * 3 + (2 * 2 + (2 * 1 + 4))) +(2 * 1 + (2 * 2 + (2 * 3 + 4))) ---------------------------------------------------- -- 7. Data Types @@ -425,7 +426,7 @@ qsort (p:xs) = qsort lesser ++ [p] ++ qsort greater greater = filter (>= p) xs ``` -Haskell is easy to install. Get it [here](http://www.haskell.org/platform/). +There are two popular ways to install Haskell: The traditional [Cabal-based installation](http://www.haskell.org/platform/), and the newer [Stack-based process](https://www.stackage.org/install). You can find a much gentler introduction from the excellent [Learn you a Haskell](http://learnyouahaskell.com/) or |