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diff --git a/purescript.html.markdown b/purescript.html.markdown index a006cdff..61287ceb 100644 --- a/purescript.html.markdown +++ b/purescript.html.markdown @@ -2,194 +2,207 @@ 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/) -```haskell +```purescript -- -- 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 +> 0xff + 1 -- 256 -- Unary negation -6 * -3 -- -18 -6 * negate 3 -- -18 --- Modulus -3 % 2 -- 1 -4 % 2 -- 0 +> 6 * -3 -- -18 +> 6 * negate 3 -- -18 +-- Modulus, from purescript-math (Math) +> 3.0 % 2.0 -- 1.0 +> 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 +> true :: Boolean -- true +> false :: Boolean -- false -- Negation -not true --false -23 == 23 -- true -1 /= 4 -- true -1 >= 4 -- false +> not true -- false +> 23 == 23 -- true +> 1 /= 4 -- true +> 1 >= 4 -- false -- Comparisions < <= > >= -- are defined in terms of compare -compare 1 2 -- LT -compare 2 2 -- EQ -compare 3 2 -- GT +> compare 1 2 -- LT +> compare 2 2 -- EQ +> compare 3 2 -- GT -- Conjunction and Disjunction -true && (9 >= 19 || 1 < 2) -- true +> true && (9 >= 19 || 1 < 2) -- true -- Strings -"Hellow" :: String -- "Hellow" --- Multiline string -"Hellow\ +> "Hellow" :: String -- "Hellow" +-- 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" +> "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] -[true, true, false] :: [Boolean] -- [true,true,false] +> [1,1,2,3,5,8] :: Array Number -- [1,1,2,3,5,8] +> [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] +> 1 : [2,4,3] -- [1,2,4,3] -- Requires purescript-arrays (Data.Array) -- and purescript-maybe (Data.Maybe) -- Safe access return Maybe a -head [1,2,3] -- Just (1) -tail [3,2,1] -- Just ([2,1]) -init [1,2,3] -- Just ([1,2]) -last [3,2,1] -- Just (1) +> head [1,2,3] -- Just (1) +> tail [3,2,1] -- Just ([2,1]) +> init [1,2,3] -- Just ([1,2]) +> last [3,2,1] -- Just (1) -- Random access - indexing -[3,4,5,6,7] !! 2 -- Just (5) +> [3,4,5,6,7] !! 2 -- Just (5) -- Range -1..5 -- [1,2,3,4,5] -length [2,2,2] -- 3 -drop 3 [5,4,3,2,1] -- [2,1] -take 3 [5,4,3,2,1] -- [5,4,3] -append [1,2,3] [4,5,6] -- [1,2,3,4,5,6] +> 1..5 -- [1,2,3,4,5] +> length [2,2,2] -- 3 +> drop 3 [5,4,3,2,1] -- [2,1] +> take 3 [5,4,3,2,1] -- [5,4,3] +> 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 -let book = {title: "Foucault's pendulum", author: "Umberto Eco"} +-- 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" +> 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" +> 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} -changeTitle book "Ill nome della rosa" -- {title: "Ill nome della - -- rosa", author: "Umberto Eco"} +> let changeTitle b t = b {title = t} +> getTitle (changeTitle book "Ill nome della rosa") -- "Ill nome della rosa" -- -- 4. Functions -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 --- top level binding -mod x y = x % y -mod 3 2 -- 1 +-- In psci's multiline mode +> let sumOfSquares :: Int -> Int -> Int + sumOfSquares x y = x*x + y*y +> sumOfSquares 3 4 -- 25 +> let myMod x y = x % y +> myMod 3.0 2.0 -- 1.0 -- Infix application of function -3 `mod` 2 -- 1 +> 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 +> sumOfSquares 3 4 * sumOfSquares 4 5 -- 1025 -- Conditional -abs' n = if n>=0 then n else -n -abs' (-3) -- 3 +> let abs' n = if n>=0 then n else -n +> abs' (-3) -- 3 -- Guarded equations -abs n | n >= 0 = n - | otherwise = -n +> let abs'' n | n >= 0 = n + | otherwise = -n -- Pattern matching --- Note the type signature, input is an array of numbers The pattern --- matching destructures and binds the array into parts -first :: [Number] -> Number -first (x:_) = x -first [3,4,5] -- 3 -second :: [Number] -> Number -second (_:y:_) = y -second [3,4,5] -- 4 -sumTwo :: [Number] -> [Number] -sumTwo (x:y:rest) = (x+y) : rest -sumTwo [2,3,4,5,6] -- [5,4,5,6] - --- sumTwo doesn't handle when the array is empty or just have one --- element in which case you get an error +-- Note the type signature, input is a list of numbers. The pattern matching +-- destructures and binds the list into parts. +-- Requires purescript-lists (Data.List) +> let first :: forall a. List a -> a + first (Cons x _) = x +> first (toList [3,4,5]) -- 3 +> let second :: forall a. List a -> a + second (Cons _ (Cons y _)) = y +> second (toList [3,4,5]) -- 4 +> let sumTwo :: List Int -> List Int + 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 list is empty or there's only one element in +-- which case you get an error. sumTwo [1] -- Failed pattern match -- Complementing patterns to match -- Good ol' Fibonacci -fib 1 = 1 -fib 2 = 2 -fib x = fib (x-1) + fib (x-2) -fib 10 -- 89 +> let fib 1 = 1 + fib 2 = 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 -isZero _ = false +> let isZero 0 = true + isZero _ = false -- Pattern matching on records -ecoTitle {author = "Umberto Eco", title = t} = Just t -ecoTitle _ = Nothing +> let ecoTitle {author = "Umberto Eco", title = t} = Just t + ecoTitle _ = Nothing -ecoTitle book -- Just ("Foucault's pendulum") -ecoTitle {title: "The Quantum Thief", author: "Hannu Rajaniemi"} -- 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 +> (\x -> x*x) 3 -- 9 +> (\x y -> x*x + y*y) 4 5 -- 41 +> let sqr = \x -> x*x -- Currying -add x y = x + y -- is equivalent with -add = \x -> (\y -> x+y) -add3 = add 3 -:t add3 -- Prim.Number -> Prim.Number +> let myAdd x y = x + y -- is equivalent with +> let myAdd' = \x -> \y -> x + y +> let add3 = myAdd 3 +> :t add3 -- Prim.Int -> Prim.Int -- Forward and backward function composition -- drop 3 followed by taking 5 -(drop 3 >>> take 5) (1..20) -- [4,5,6,7,8] +> (drop 3 >>> take 5) (1..20) -- [4,5,6,7,8] -- take 5 followed by dropping 3 -(drop 3 <<< take 5) (1..20) -- [4,5] +> (drop 3 <<< take 5) (1..20) -- [4,5] -- Operations using higher order functions -even x = x % 2 == 0 -filter even (1..10) -- [2,4,6,8,10] -map (\x -> x+11) (1..5) -- [12,13,14,15,16] +> 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] -- Requires purescript-foldable-traversabe (Data.Foldable) -foldr (+) 0 (1..10) -- 55 -sum (1..10) -- 55 -product (1..10) -- 3628800 +> foldr (+) 0 (1..10) -- 55 +> sum (1..10) -- 55 +> product (1..10) -- 3628800 -- Testing with predicate -any even [1,2,3] -- true -all even [1,2,3] -- false +> any even [1,2,3] -- true +> all even [1,2,3] -- false ``` |