mirror of
https://github.com/adambard/learnxinyminutes-docs.git
synced 2024-11-26 20:34:32 +03:00
updated purescript example for compiler version >= 0.7.4.1
This commit is contained in:
thimoteus
parent
070e53dd85
commit
e44d7d47ec
@ -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]
|
||||
-- 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 array is empty or just have one
|
||||
-- element in which case you get an error
|
||||
-- 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
|
||||
|
||||
```
|
||||
|
||||
|
||||
Loading…
Reference in New Issue
Block a user