summaryrefslogtreecommitdiffhomepage
path: root/purescript.html.markdown
diff options
context:
space:
mode:
authorthimoteus <thimoteus@teknik.io>2015-10-13 01:25:56 -0700
committerthimoteus <thimoteus@teknik.io>2015-10-13 01:25:56 -0700
commitc2f15ffd87b116b17244fe6053f385d7cb4dabf0 (patch)
treea3eb9161a30be3050dd341052e0787aa00f98e06 /purescript.html.markdown
parente44d7d47ec1fd01cb7ec8054fd59fc0ee3987476 (diff)
readded haskell syntax highlighting, added line about running examples in psci, removed >'s
Diffstat (limited to 'purescript.html.markdown')
-rw-r--r--purescript.html.markdown193
1 files changed, 98 insertions, 95 deletions
diff --git a/purescript.html.markdown b/purescript.html.markdown
index 61287ceb..6d8cfbb9 100644
--- a/purescript.html.markdown
+++ b/purescript.html.markdown
@@ -11,142 +11,145 @@ PureScript is a small strongly, statically typed language compiling to Javascrip
* Documentation: [http://pursuit.purescript.org/](http://pursuit.purescript.org/)
* Book: Purescript by Example, [https://leanpub.com/purescript/](https://leanpub.com/purescript/)
-```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
+import Prelude
-- Numbers
-> 1.0 + 7.2*5.5 :: Number -- 40.6
+1.0 + 7.2*5.5 :: Number -- 40.6
-- Ints
-> 1 + 2*5 :: Int -- 11
+1 + 2*5 :: Int -- 11
-- Types are inferred, so the following works fine
-> 9.0/2.5 + 4.4 -- 8.0
+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
+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
+6 * -3 -- -18
+6 * negate 3 -- -18
-- Modulus, from purescript-math (Math)
-> 3.0 % 2.0 -- 1.0
-> 4.0 % 2.0 -- 0.0
+3.0 % 2.0 -- 1.0
+4.0 % 2.0 -- 0.0
-- Inspect the type of an expression in psci
-> :t 9.5/2.5 + 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"
+"Hellow" :: String -- "Hellow"
-- Multiline string without newlines, to run in psci use the --multi-line-mode flag
-> "Hellow\
+"Hellow\
\orld" -- "Helloworld"
-- Multiline string with newlines
-> """Hello
+"""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] :: Array Number -- [1,1,2,3,5,8]
-> [true, true, false] :: Array 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.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.
-- 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"}
+let book = {title: "Foucault's pendulum", author: "Umberto Eco"}
-- Access properties
-> book.title -- "Foucault's pendulum"
+book.title -- "Foucault's pendulum"
-> let 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"
+_.title book -- "Foucault's pendulum"
-- Update a record
-> let changeTitle b t = b {title = t}
-> getTitle (changeTitle book "Ill nome della rosa") -- "Ill nome della rosa"
+let changeTitle b t = b {title = t}
+getTitle (changeTitle book "Ill nome della rosa") -- "Ill nome della rosa"
--
-- 4. Functions
-- 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
+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 has higher precedence than all other
-- operators
-> sumOfSquares 3 4 * sumOfSquares 4 5 -- 1025
+sumOfSquares 3 4 * sumOfSquares 4 5 -- 1025
-- Conditional
-> let 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
-> let abs'' n | n >= 0 = n
- | otherwise = -n
+let abs'' n | n >= 0 = n
+ | otherwise = -n
-- Pattern matching
-- 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]
+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.
@@ -154,55 +157,55 @@ sumTwo [1] -- Failed pattern match
-- Complementing patterns to match
-- Good ol' Fibonacci
-> let 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
-> let isZero 0 = true
- isZero _ = false
+let isZero 0 = true
+ isZero _ = false
-- Pattern matching on records
-> let 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 lacks required 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
-> let sqr = \x -> x*x
+(\x -> x*x) 3 -- 9
+(\x y -> x*x + y*y) 4 5 -- 41
+let sqr = \x -> x*x
-- Currying
-> 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
+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
-> 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]
+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
```