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| == Ch1 有型別的函數式程設 == | | == Ch1 有型別的函數式程設 == |
| ===1.1介紹===
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| <pre>(* 我是註解 *)
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| print_endline "string" (* 函數使用，一般寫法：print_endline("string")*)
| | * [[Program=Proof筆記-第1章]] |
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| </pre>
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|
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| ocamlopt 可以編譯
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|
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| <pre>
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|
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| # 2 + 2 ;;
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| -: int = 4
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| (* 對結果做型別推導 *)
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|
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| let s = string_to_int 3.2
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| (* -> 這會型別錯誤 *)
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| </pre>
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|
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| ====Type annotation（型別顯式標記）====
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|
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| 比較：
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| <pre>
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| let f x = x + 1
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| let f (x : int ) : int = x + 1
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|
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| </pre>
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|
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| ====型別====
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|
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| List.map 的型別：<code>('a -> 'b) -> 'a list -> 'b list</code>
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| <code>let mapped_list = List.map (fun x -> 2 * x) a_list</code>
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|
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| ====可變變數(reference)====
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| <pre>
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| let () =
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| let r = ref 0 in (* 可變 reference *)
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| for i = 0 to 9 do
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| r := !r + 1 (* 刷新 r 值，使其 + 1）
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| done
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|
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| </pre>
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| 另外還有 record、array、GADT、垃圾回收等等。
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|
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| ===1.2基本操作===
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| <pre>
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| let () = print_string "foo" (*回傳 unit*)
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| </pre>
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| ==== 迴圈====
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| <pre>
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| let () =
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| let r = ref 0 in
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| for i = 0 to 9 do
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| r := !r +1
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| done
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| </pre>
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|
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| ====部分應用（不需括號）====
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|
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| int -> (int -> int) 即 int -> int -> int
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|
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| add 的以下寫法：
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| <pre>
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| add x y = x + y
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| add y = fn x -> x + y
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| add = fn x y -> x + y
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| </pre>
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|
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| ====互遞迴====
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| <pre>
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| let rec f x = ...
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| and g x = .....
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| </pre>
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|
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| ====布林 boolean 操作====
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|
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| 操作子
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| <pre>
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| && || not
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|
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| 條件與區塊
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| <pre>
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| if ... then ... else...
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| while ... do ... done
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| </pre>
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|
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| 比對操作子
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| <pre>
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| == 同一記憶體位置
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| = 值相等
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| <> 不等於
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| </pre>
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|
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| ====product type====
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| add (x, y) = x + y
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|
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| (int * int) -> int，其中的 (int * int)是 product type
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|
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| ====list====
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| *[]：nil
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| *x::ls：(cons x ls)
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| *x1@x2：concat x1 and x2
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| *List.length：字串長度
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| *List.map：map
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| *List.iter：execute a funct90n for list
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| *List.mem：成員是否在列表內
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|
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| ==== String ====
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| "foo"
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|
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| ====Unit====
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| unit : ()
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|
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| <pre>
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| let f = print_string "foo" (* let f = printString("foo"); *)
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| let f () = print_string "foo" (* let f = function () { printString("foo") ;}*)
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| </pre>
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|
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| ===1.3遞迴型別===
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| tree型別定義如下：
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| <pre>
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| type tree =
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| | Node of int * tree * tree
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| | Leaf of int
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| </pre>
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| 以下是合規的tree
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| <pre>
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| let t = Node(3, Node(4, Leaf 1, Leaf 3))
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| </pre>
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|
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| ====模式比對====
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| <pre>
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| let sum foo x =
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| match x with
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| | Node (n , t1, t2) -> n + sum t1 + sum t2
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| | Leaf n -> n
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| </pre>
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|
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| guard
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| <pre>|Leaf n when n > 0 -> ...</pre>
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|
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| 語法糖
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| <pre>let f = function ... 即 let f x = match x with ...</pre>
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|
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| ====Bool====
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| <pre>type bool = True | False</pre>
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| ====List====
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| <pre>type 'a list =
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| | Nil
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| | Cons of 'a * 'a list</pre>
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|
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| ====coproducts====
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| <pre>type ('a, 'b) either =
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| | Left of 'a
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| | Right of 'b</pre>
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|
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| ====unit====
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| <pre>type unit = | T</pre>
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| 只有這個值 <code>()</code>
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|
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| ====Empty====
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| <pre>type Empty = |</pre>
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|
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| ====Natural Number====
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| <pre>type Nat =
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| |Zero
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| |Suc of nat</pre>
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| ====例外處理：Option type and exception====
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| 處理例外的方式
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| Option type
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| <pre>type 'a option =
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| | Some of 'a
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| | None
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| </pre>
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| exception
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| <pre>let hd l =
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| match l with
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| | x::l -> x
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| | [] -> raise Not_found</pre>
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|
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| 搭配
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| <pre>try
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| ...
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| with
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| | Not_found -> ...</pre>
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| [[分類:資訊]] | | [[分類:資訊]] |
| [[分類:邏輯學]] | | [[分類:邏輯學]] |