On 03/18/2013 03:23 PM, Chris Angelico wrote:
The languages that permit you to assign to a function call all have
some notion of a reference type.

Assigning to function calls is orthogonal to reference types. For example, Python manages assignment to subscripts without having references just fine:

val = obj[index]      # val = obj.__getitem__(index)
obj[index] = val      # obj.__setitem__(index, val)

In analogy with that, Python could implement what looks like assignment to function call like this:

val = f(arg)          # val = f.__call__(arg)
f(arg) = val          # f.__setcall__(arg, val)

I am not arguing that this should be added, I'm only pointing out that Python's object customization is not fundamentally at odds with assignment to function calls. Having said that, I am in fact arguing that Python doesn't need them. All C++ uses of operator() overloads can be implemented with the subscript operator.

Even if one needs more different assignments than there are operators, Python can provide it as easily as C++. For example, on std::vector::operator[] provides access to the container without error checking, and std::vector::at() checks bounds:

vec[i] = val      // no error checking
vec.at(i) = val   // error checking

This is trivially translated to Python as:

vec[i] = val      # primary functionality, use __setitem__
vec.at[i] = val   # secondary functionality, __setitem__ on a proxy

_______________________________________________
Python-Dev mailing list
Python-Dev@python.org
http://mail.python.org/mailman/listinfo/python-dev
Unsubscribe: 
http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com

Reply via email to