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-rw-r--r--haskell.html.markdown36
1 files changed, 18 insertions, 18 deletions
diff --git a/haskell.html.markdown b/haskell.html.markdown
index 79fbf09f..2f807c5f 100644
--- a/haskell.html.markdown
+++ b/haskell.html.markdown
@@ -148,12 +148,12 @@ add 1 2 -- 3
-- Guards: an easy way to do branching in functions
fib x
- | x < 2 = x
+ | x < 2 = 1
| otherwise = fib (x - 1) + fib (x - 2)
-- Pattern matching is similar. Here we have given three different
-- definitions for fib. Haskell will automatically call the first
--- function that matches the pattern of the value.
+-- function that matches the pattern of the value.
fib 1 = 1
fib 2 = 2
fib x = fib (x - 1) + fib (x - 2)
@@ -181,7 +181,7 @@ foldl1 (\acc x -> acc + x) [1..5] -- 15
----------------------------------------------------
-- partial application: if you don't pass in all the arguments to a function,
--- it gets "partially applied". That means it returns a function that takes the
+-- it gets "partially applied". That means it returns a function that takes the
-- rest of the arguments.
add a b = a + b
@@ -319,13 +319,13 @@ Nothing -- of type `Maybe a` for any `a`
-- called. It must return a value of type `IO ()`. For example:
main :: IO ()
-main = putStrLn $ "Hello, sky! " ++ (say Blue)
+main = putStrLn $ "Hello, sky! " ++ (say Blue)
-- putStrLn has type String -> IO ()
--- It is easiest to do IO if you can implement your program as
--- a function from String to String. The function
+-- It is easiest to do IO if you can implement your program as
+-- a function from String to String. The function
-- interact :: (String -> String) -> IO ()
--- inputs some text, runs a function on it, and prints out the
+-- inputs some text, runs a function on it, and prints out the
-- output.
countLines :: String -> String
@@ -339,43 +339,43 @@ main' = interact countLines
-- the `do` notation to chain actions together. For example:
sayHello :: IO ()
-sayHello = do
+sayHello = do
putStrLn "What is your name?"
name <- getLine -- this gets a line and gives it the name "name"
putStrLn $ "Hello, " ++ name
-
+
-- Exercise: write your own version of `interact` that only reads
-- one line of input.
-
+
-- The code in `sayHello` will never be executed, however. The only
--- action that ever gets executed is the value of `main`.
--- To run `sayHello` comment out the above definition of `main`
+-- action that ever gets executed is the value of `main`.
+-- To run `sayHello` comment out the above definition of `main`
-- and replace it with:
-- main = sayHello
--- Let's understand better how the function `getLine` we just
+-- Let's understand better how the function `getLine` we just
-- used works. Its type is:
-- getLine :: IO String
-- You can think of a value of type `IO a` as representing a
--- computer program that will generate a value of type `a`
+-- computer program that will generate a value of type `a`
-- when executed (in addition to anything else it does). We can
--- store and reuse this value using `<-`. We can also
+-- store and reuse this value using `<-`. We can also
-- make our own action of type `IO String`:
action :: IO String
action = do
putStrLn "This is a line. Duh"
- input1 <- getLine
+ input1 <- getLine
input2 <- getLine
-- The type of the `do` statement is that of its last line.
- -- `return` is not a keyword, but merely a function
+ -- `return` is not a keyword, but merely a function
return (input1 ++ "\n" ++ input2) -- return :: String -> IO String
-- We can use this just like we used `getLine`:
main'' = do
putStrLn "I will echo two lines!"
- result <- action
+ result <- action
putStrLn result
putStrLn "This was all, folks!"