#12978: conditionally_defined decorator for methods and nested classes
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Reporter: nthiery | Owner: jason
Type: enhancement | Status: new
Priority: major | Milestone: sage-
Component: misc | wishlist
Keywords: categories, | Resolution:
conditionally_defined | Merged in:
Authors: | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
Dependencies: | Stopgaps:
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Comment (by SimonKing):
The problem with nested classes is that, if you define
{{{
class C:
__metaclass__ = NestedClassMetaclass
class D:
pass
}}}
then ''during creation of C'' (`NestedClassMetaclass.__init__(C)`) all
attributes of C that are classes get their names changed (here: It becomes
"C.D" instead of "D"). But if you pack the nested class into a
conditionally_defined decorator, then `NestedClassMetaclass.__init__(C)`
will not realise that D is a class, and will thus not change the name.
Moreover, at least in the current implementation, the
conditionally_defined decorator operates with the name of the wrapped
object. But if this name is not a valid attribute name (such as `"C.D"`)
then the whole construction will fail anyway.
In any case, I think it would be more interesting to be able to
conditionally define a cached method, in ''both'' versions I suggested:
{{{
@cached_method
@conditionally_defined(...):
def meth(...):
...
}}}
being a cached method whose underlying implementation is conditional, and
{{{
@conditionally_defined(...):
@cached_method
def meth(...):
...
}}}
being a cached method that is only used conditionally.
--
Ticket URL: <http://trac.sagemath.org/ticket/12978#comment:14>
Sage <http://www.sagemath.org>
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