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54 lines
1.6 KiB
Markdown
54 lines
1.6 KiB
Markdown
# 數組
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[](https://gezf7g7pd5.execute-api.ap-northeast-1.amazonaws.com/default/source_up_to_date?owner=erg-lang&repos=erg&ref=main&path=doc/EN/syntax/10_array.md&commit_hash=603abbd5fa3f8baffe0d614758e1a554705e6732)
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數組是最基本的__collection(聚合)__
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集合是一個可以在其中包含多個對象的對象
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```python
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a = [1, 2, 3]
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a: [Int; 3] # 類型說明: 分號后的數字為元素個數
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# 如果元素個數未知，可以省略
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a: [Int]
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mut_a = [!1, !2, !3]
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mut_a[0].inc!()
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assert mut_a == [2, 2, 3]
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```
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通常，數組不能包含不同類型的對象
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```python.
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[1, "a"] # 類型錯誤: 第一個元素是 Int，但第二個元素是 Str
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```
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但是，您可以通過像這樣顯式指定類型來繞過限制
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```python,compile_fail
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[1: Int or Str, "a"]
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```
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## 切片
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一個數組也可以同時取出多個值。這稱為切片
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```python
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l = [1, 2, 3, 4]
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# 與 Python 中的 l[1:3] 相同
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assert l[1.. <3] == [2, 3]
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assert l[1..2] == [2, 3]
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# 與 l[1] 相同
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assert l[1..1] == [2]
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# 與 Python 中的 l[::2] 相同
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assert l[..].step(2) == [2, 4]
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```
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通過切片獲得的對象是數組的(不可變的)副本
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```python
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print! Typeof l[1..2] # [Int; 4]
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```
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<p align='center'>
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<a href='./09_builtin_procs.md'>上一頁</a> | <a href='./11_tuple.md'>下一頁</a>
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</p>
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