Merge pull request #1486 from Thimoteus/master

updated purescript example for compiler version >= 0.7.4.1

purescript.html.markdown

@@ -2,40 +2,49 @@
 language: purescript
 contributors:
     - ["Fredrik Dyrkell", "http://www.lexicallyscoped.com"]
+    - ["Thimoteus", "https://github.com/Thimoteus"]
 ---
 
 PureScript is a small strongly, statically typed language compiling to Javascript.
 
 * Learn more at [http://www.purescript.org/](http://www.purescript.org/)
-* Documentation: [http://docs.purescript.org/en/latest/](http://docs.purescript.org/en/latest/)
+* Documentation: [http://pursuit.purescript.org/](http://pursuit.purescript.org/)
 * Book: Purescript by Example, [https://leanpub.com/purescript/](https://leanpub.com/purescript/)
 
+All the noncommented lines of code can be run in the PSCI REPL, though some will
+require the `--multi-line-mode` flag.
+
 ```haskell
 
 --
 -- 1. Primitive datatypes that corresponds to their Javascript
 -- equivalents at runtime.
 
+import Prelude
 -- Numbers
-1 + 7*5 :: Number -- 36
+1.0 + 7.2*5.5 :: Number -- 40.6
+-- Ints
+1 + 2*5 :: Int -- 11
 -- Types are inferred, so the following works fine
-9 / 2.5 + 4.4 -- 8
+9.0/2.5 + 4.4 -- 8.0
+-- But Ints and Numbers don't mix, so the following won't
+5/2 + 2.5 -- Expression 2.5 does not have type Int
 -- Hexadecimal literals
 0xff + 1 -- 256
 -- Unary negation
 6 * -3 -- -18
 6 * negate 3 -- -18
--- Modulus
+-- Modulus, from purescript-math (Math)
-3 % 2 -- 1
+3.0 % 2.0 -- 1.0
-4 % 2 -- 0
+4.0 % 2.0 -- 0.0
 -- Inspect the type of an expression in psci
-:t 9 / 2.5 + 4.4 -- Prim.Number
+:t 9.5/2.5 + 4.4 -- Prim.Number
 
 -- Booleans
 true :: Boolean -- true
 false :: Boolean -- false
 -- Negation
-not true --false
+not true -- false
 23 == 23 -- true
 1 /= 4 -- true
 1 >= 4 -- false
@@ -49,19 +58,22 @@ true && (9 >= 19 || 1 < 2) -- true
 
 -- Strings
 "Hellow" :: String -- "Hellow"
--- Multiline string
+-- Multiline string without newlines, to run in psci use the --multi-line-mode flag
 "Hellow\
 \orld" -- "Helloworld"
+-- Multiline string with newlines
+"""Hello 
+world""" -- "Hello\nworld"
 -- Concatenate
 "such " ++ "amaze" -- "such amaze"
 
 --
 -- 2. Arrays are Javascript arrays, but must be homogeneous
 
-[1,1,2,3,5,8] :: [Number] -- [1,1,2,3,5,8]
+[1,1,2,3,5,8] :: Array Number -- [1,1,2,3,5,8]
-[true, true, false] :: [Boolean] -- [true,true,false]
+[true, true, false] :: Array Boolean -- [true,true,false]
 -- [1,2, true, "false"] won't work
--- `Cannot unify Prim.Number with Prim.Boolean`
+-- `Cannot unify Prim.Int with Prim.Boolean`
 -- Cons (prepend)
 1 : [2,4,3] -- [1,2,4,3]
 
@@ -84,91 +96,95 @@ append [1,2,3] [4,5,6] -- [1,2,3,4,5,6]
 
 --
 -- 3. Records are Javascript objects, with zero or more fields, which
--- can have different types
+-- can have different types.
+-- In psci you have to write `let` in front of the function to get a
+-- top level binding.
 let book = {title: "Foucault's pendulum", author: "Umberto Eco"}
 -- Access properties
 book.title -- "Foucault's pendulum"
 
-getTitle b = b.title
+let getTitle b = b.title
 -- Works on all records with a title (but doesn't require any other field)
 getTitle book -- "Foucault's pendulum"
 getTitle {title: "Weekend in Monaco", artist: "The Rippingtons"} -- "Weekend in Monaco"
+-- Can use underscores as shorthand
+_.title book -- "Foucault's pendulum"
 -- Update a record
-changeTitle b t = b {title = t}
+let changeTitle b t = b {title = t}
-changeTitle book "Ill nome della rosa" -- {title: "Ill nome della
+getTitle (changeTitle book "Ill nome della rosa") -- "Ill nome della rosa"
-  -- rosa", author: "Umberto Eco"}
 
 --
 -- 4. Functions
-sumOfSquares x y = x*x+y*y
+-- In psci's multiline mode
+let sumOfSquares :: Int -> Int -> Int
+    sumOfSquares x y = x*x + y*y
 sumOfSquares 3 4 -- 25
--- In psci you have to write `let` in front of the function to get a
+let myMod x y = x % y
--- top level binding
+myMod 3.0 2.0 -- 1.0
-mod x y = x % y
-mod 3 2 -- 1
 -- Infix application of function
 3 `mod` 2 -- 1
 
--- function application have higher precedence than all other
+-- function application has higher precedence than all other
 -- operators
 sumOfSquares 3 4 * sumOfSquares 4 5 -- 1025
 
 -- Conditional
-abs' n = if n>=0 then n else -n
+let abs' n = if n>=0 then n else -n
 abs' (-3) -- 3
 
 -- Guarded equations
-abs n | n >= 0    = n
+let abs'' n | n >= 0    = n
-      | otherwise = -n
+            | otherwise = -n
 
 -- Pattern matching
 
--- Note the type signature, input is an array of numbers The pattern
+-- Note the type signature, input is a list of numbers. The pattern matching
--- matching destructures and binds the array into parts
+-- destructures and binds the list into parts.
-first :: [Number] -> Number
+-- Requires purescript-lists (Data.List)
-first (x:_) = x
+let first :: forall a. List a -> a
-first [3,4,5] -- 3
+    first (Cons x _) = x
-second :: [Number] -> Number
+first (toList [3,4,5]) -- 3
-second (_:y:_) = y
+let second :: forall a. List a -> a
-second [3,4,5] -- 4
+    second (Cons _ (Cons y _)) = y
-sumTwo :: [Number] -> [Number]
+second (toList [3,4,5]) -- 4
-sumTwo (x:y:rest) = (x+y) : rest
+let sumTwo :: List Int -> List Int
-sumTwo [2,3,4,5,6] -- [5,4,5,6]
+    sumTwo (Cons x (Cons y rest)) = x + y : rest
+fromList (sumTwo (toList [2,3,4,5,6])) :: Array Int -- [5,4,5,6]
 
--- sumTwo doesn't handle when the array is empty or just have one
+-- sumTwo doesn't handle when the list is empty or there's only one element in
--- element in which case you get an error
+-- which case you get an error.
 sumTwo [1] -- Failed pattern match
 
 -- Complementing patterns to match
 -- Good ol' Fibonacci
-fib 1 = 1
+let fib 1 = 1
-fib 2 = 2
+    fib 2 = 2
-fib x = fib (x-1) + fib (x-2)
+    fib x = fib (x-1) + fib (x-2)
 fib 10 -- 89
 
 -- Use underscore to match any, where you don't care about the binding name
-isZero 0 = true
+let isZero 0 = true
-isZero _ = false
+    isZero _ = false
 
 -- Pattern matching on records
-ecoTitle {author = "Umberto Eco", title = t} = Just t
+let ecoTitle {author = "Umberto Eco", title = t} = Just t
-ecoTitle _ = Nothing
+    ecoTitle _ = Nothing
 
 ecoTitle book -- Just ("Foucault's pendulum")
 ecoTitle {title: "The Quantum Thief", author: "Hannu Rajaniemi"} -- Nothing
 -- ecoTitle requires both field to type check:
-ecoTitle {title: "The Quantum Thief"} -- Object does not have property author
+ecoTitle {title: "The Quantum Thief"} -- Object lacks required property "author"
 
 -- Lambda expressions
 (\x -> x*x) 3 -- 9
 (\x y -> x*x + y*y) 4 5 -- 41
-sqr = \x -> x*x
+let sqr = \x -> x*x
 
 -- Currying
-add x y = x + y -- is equivalent with
+let myAdd x y = x + y -- is equivalent with
-add = \x -> (\y -> x+y)
+let myAdd' = \x -> \y -> x + y
-add3 = add 3
+let add3 = myAdd 3
-:t add3 -- Prim.Number -> Prim.Number
+:t add3 -- Prim.Int -> Prim.Int
 
 -- Forward and backward function composition
 -- drop 3 followed by taking 5
@@ -177,9 +193,9 @@ add3 = add 3
 (drop 3 <<< take 5) (1..20) -- [4,5]
 
 -- Operations using higher order functions
-even x = x % 2 == 0
+let even x = x `mod` 2 == 0
 filter even (1..10) -- [2,4,6,8,10]
-map (\x -> x+11) (1..5) -- [12,13,14,15,16]
+map (\x -> x + 11) (1..5) -- [12,13,14,15,16]
 
 -- Requires purescript-foldable-traversabe (Data.Foldable)