python 3中具有类似lisp的通用函数的包。
gf3的Python项目详细描述
概述
gf允许您编写泛型函数 generic functions 有了多个方法，就可以分派所有的参数。
简单示例
>>> from gf import generic, method >>> add = generic() >>> type(add) <class 'function'>
让我们为两个整数定义add：
>>> @method() ... def add(n0: int, n1: int): ... return n0 + n1
让我们测试一下：
>>> add(1, 2) 3
使用其他类型的实例调用add失败：
>>> add("Hello ", "World")
Traceback (most recent call last):
...
NotImplementedError: Generic '__main__.add' has no implementation for type(s): __builtin__.str, __builtin__.str
当然，add也可以定义为两个字符串：
>>> @method() ... def add(s0: str, s1: str): ... return s0 + s1
现在我们的hello world示例可以工作了：
>>> add("Hello ", "World")
'Hello World'
add也可以为字符串和整数定义：
>>> @method() ... def add(s: str, n: int): ... return s + str(n)
因此，我们可以添加一个字符串和一个数字：
>>> add("You ", 2)
'You 2'
python的特殊方法
gf.object将（几乎）所有special instance methods of a python object作为泛型函数实现。 该包包括一个rational number实现，它使 大量使用此功能：
@method()def__add__(a:object,b:Rational):"""Add an object and a rational number. `a` is converted to a `Rational` and then both are added."""returnRational(a)+b@method(Rational,object)def__add__(a:Rational,b:object):"""Add a rational number and an object. `b` is converted to a `Rational` and then both are added."""returna+Rational(b)
gf.object还有一种更简单的覆盖方法
对象。
@method()def__out__(rational:Rational,writer:Writer):"""Write a nice representation of the rational. Denominators that equal 1 are not printed."""writer("%d",rational.numerator)ifrational.denominator!=1:writer(" / %d",rational.denominator)@method()def__spy__(rational:Rational,writer:Writer):"""Write a debug representation of the rational."""writer("%s(",rational.__class__.__name__)ifrational.numerator!=0:writer("%r",rational.numerator)ifrational.denominator!=1:writer(", %r",rational.denominator)writer(")")
安装
像往常一样，gf3可以用pip安装，如下所示：
pip install gf3
变化
每个版本中所做更改的简短草图。
释放0.2.4
在0.2.4版中更改了以下内容：
- The push-method accepts an identation string for identing writers.
- The methods push and pop now accept arbitrary arguments in the general case.
- Successfully tested the whole framework with Python 3.5.
版本0.2.3
在0.2.3版中更改了以下内容：
- Fixed the long description.
- Wrote some documentation about changing the implementation class of a generic function.
版本0.2.2
在0.2.2版中更改了以下内容：
- Write more documentation. Especially documented the merge and the isgeneric functions.
- Consistency between the long text and on PyPi and the documentation.
版本0.2.1
需要碰撞版本信息，因为主页 包中的信息是错误的[1]，需要新的上载。
释放0.2.0
在0.2.0版中更改了以下内容：
- Ported the whole module to Python 3.6 and Python 3.7.
- Exclusively uses parameter annotations to specify the types to dispatch on.
- Added standard conforming default implementations for methods like __add__. All these methods now raise a proper TypeError instead of raising a NotImplementedError.
- Added some means to write generic functions that dispatch types only. This is the generic function equivalent of a class-method.
- Added some means to dispatch on single objects. This is the equivalent adding methods to class-instances [2].
- The package name for PyPi is now ^{tt1}$.
释放0.1.4
以下内容已在0.1.4版中修复：
- Fixed an issue with variadic methods. Sometimes definitions of variadic methods added after the method was already called where not added.
- Specified and implemented a precedence rule for overlapping variadic methods of generic functions.
- Improved generated documentation for variadic methods.
- Fixed the markup of some notes in the documentation.
版本0.1.3
以下内容在0.1.3版中已更改：
- Added variadic methods, e.g. multi-methods with a variable number of arguments.
- Improved the long description text a bit and fixed bug in its markup.
- Fixed invalid references in the long description.
版本0.1.2
在0.1.2版中更改了以下内容：
- Added a generic functions for gf.Object.__call__.
- Added a gf.go.FinalizingMixin.
- gf.generic now also accepts a type.
- Improved the exception information for ambiguous calls.
- Fixed some documentation glitches.
致谢
guido van rossum创建了这个包的核心。我刚把一些东西改名了 还加了很多方便的东西。谢谢你圭多！
版权所有
版权所有2006-2013 Python软件基金会。 版权所有2013-2018 Gerald Klix。
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