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91 lines
2.3 KiB
Markdown
91 lines
2.3 KiB
Markdown
# Erg 代碼如何轉譯成 Python 代碼?
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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/compiler/transpile.md&commit_hash=13f2d31aee9012f60b7a40d4b764921f1419cdfe)
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準確地說，Erg 代碼是被轉譯為 Python 字節碼。鑒于 Python 字節碼幾乎可以被重構為 Python 文本代碼，因此這里以等效的 Python 代碼為例。
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順便說一下，這里展示的示例是低優化級別。更高級的優化會消除不需要實例化的東西
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## 記錄，記錄類型
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它將被轉換為一個命名元組（namedtuple）。
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對于 namedtuple，請參閱 [此處](https://docs.python.org/zh-cn/3/library/collections.html#collections.namedtuple)。
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有一個類似的功能，數據類（dataclass），但由于__eq__和__hash__的自動實現，數據類在性能上略有下降
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```python
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Employee = Class {.name = Str; .id = Int}
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employee = Employee.new({.name = "John Smith"; .id = 100})
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assert employee.name == "John Smith"
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```
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```python
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from typing import NamedTuple
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class Employee(NamedTuple):
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__records__ = ['name', 'id']
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name: str
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id: int
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employee = Employee('John Smith', 100)
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assert employee.name == 'John Smith'
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```
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如果可以進一步優化，它還將被轉換為簡單的元組。
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## 多態類型
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> 在制品
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## 即時范圍
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如果沒有發生命名空間沖突，它只會被破壞和擴展
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`x::y` 等名稱在字節碼中使用，不能與 Python 代碼關聯，但如果強制表示，則會如下所示
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```python
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x =
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y = 1
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y+1
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```
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```python
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x::y = 1
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x = x::y + 1
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```
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萬一發生沖突，定義和使用只能在內部引用的函數
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```python
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x =
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y = 1
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y+1
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```
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```python
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def _():
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x=1
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y = x
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return y + 1
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x = _()
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```
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## 可見性
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它對公共變量沒有任何作用，因為它是 Python 的默認值
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私有變量由 mangling 處理
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```python
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x=1
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y =
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x = 2
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assert module::x == 2
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```
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```python
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module::x = 1
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y::x = 2
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assert module::x == 2
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y = None
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```
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