gf 0.1.4

简单示例

>>> from gf import generic, method
>>> add = generic()
>>> type(add)
<type 'function'>

让我们为两个整数定义add：

>>> @method(int, int)
... def add(n0, n1):
...     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(basestring, basestring)
... def add(s0, s1):
...     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(basestring, int)
... def add(s, n):
...     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(object,Rational)def__add__(a,b):"""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,b):"""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。和对象。使用类似文件的对象。 同样，rational示例对它的使用具有指导意义。

@method(Rational,Writer)def__out__(rational,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(Rational,Writer)def__spy__(rational,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(")")

变化

每个版本中所做更改的简短草图。