202 lines
3.2 KiB
Markdown
202 lines
3.2 KiB
Markdown
# Idea 1
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var x = 20
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val y = 30
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type Something = ...
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Something s1 = ...
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Something s2 = s1
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// Passes `some` by reference, but it's immutable. Cannot call mutable methods
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// or use it in mutable operations
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fun do_something(Something some) -> Bool {}
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do_something(s1)
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// Passes `some` by reference, and it's mutable. Can call mutable methods
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// or use it in mutable operations
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fun do_something(&Something some) -> Bool {}
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do_something(&s1)
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var arr1 = Array(10, 20, 30)
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var arr2 = &arr1
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Owned/Reference Mutable
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Type Owned n
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&Type Reference n
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mut Type Owned y
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&mut Type Reference y
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Copy/Reference Mutable Equivalent
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Some Copy n 1 (technically) references the other data
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&Some Reference n 1 References the other data
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mut Some Copy y 2 Creates a __mutable__ copy
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&mut Some Reference y 3 References the other data, __mutable__
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## `Array[A]::map`
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```thp
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fun map[B](this, (A) -> B callback) -> Array[B]
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```
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Applies `callback` to all the elements of this array, and
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returns those new values in a new array.
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### Example
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```thp
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val numbers = Array(1, 2, 3, 4, 5)
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val numbers_squared = numbers.map {it ** 2}
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print(numbers_squared) // Array(1, 4, 9, 16, 25)
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numbers.map(fun(v) {
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v - 2
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})
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```
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## `Array[A]::reduce`
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```thp
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fun reduce[B](
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this,
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B initial,
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(A previous, B current) -> B callback,
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) -> B
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```
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Iteratively reduce the array to a single value using `callback`.
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### Example
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```thp
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val numbers = Array(1, 2, 3, 4, 5)
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val sum = numbers.reduce(0, \+)
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val sum = numbers.reduce(0) {$1 + $2}
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val sum = numbers.reduce(0, fun(prev, curr) {prev + curr})
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print(sum) // 15
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```
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```thp
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val numbers = Array(1, 2, 3, 4, 5)
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val sum = numbers.reduce("", fun(prev, curr) {prev + curr})
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val sum = numbers.reduce("") {prev, curr -> prev + curr}
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print(sum) // "12345"
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```
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```thp
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// Functor
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fun fmap(
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(A) -> B,
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f[A],
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) -> f[B]
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fun (<$)(
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A,
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f[B],
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) -> f[A]
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// Applicative
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fun pure(A) -> f[A]
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fun (<*>)(
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f[A -> B],
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f[A],
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) -> f[B]
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fun (*>)(
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f[_],
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f[B],
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) -> f[B]
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fun (<*)(
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f[A],
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f[_],
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) -> f[A]
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// Monad
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fun (>>=)[m, A, B](
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m[A],
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(A) -> m[B],
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) -> m[B]
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(Array[Int], Int -> Array[String]) -> Array[String]
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val result = Array(1, 2, 3, 4, 5) >>= {Array($.into[String]())}
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print(result) // Array("1", "2", "3", "4", "5")
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```
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```thp
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Option[Int] result = "322".try_into()
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Option[Int] result_halved = result >>= {Some($ / 2)}
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print(result_halved) // Some(161)
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Option[Int] result = "abc".try_into()
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Option[Int] result_halved = result >>= {Some($ / 2)}
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print(result_halved) // None
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```
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```thp
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fun (<$>)[m, A, B](
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(A) -> B,
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m[A],
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) -> m[B]
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fun half(Int x) -> Int {
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x / 2
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}
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Option[Int] result = "322".try_into()
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Option[Int] result_halved = result <$> half
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print(result_halved) // Some(161)
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Option[Int] result = "abc".try_into()
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Option[Int] result_halved = result <$> half
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print(result_halved) // None
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```
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```thp
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fun (>>)[A, B, C](
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(A) -> B,
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(B) -> C,
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) -> (A) -> C
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val f1 = add1 >> times2
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f1(5) // 12
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```
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