On Tue, Dec 28, 2010 at 12:06:52PM -0800, Eviatar wrote:
> What is "an_element" supposed to do, exactly? Should it return the
> first item in a list, a random one, etc?
Does this help?
sage: C = Sets().parent_class
sage: C.an_element?
...
Docstring:
Returns a (preferably typical) element of this parent.
This is used both for illustration and testing purposes. If the set
``self`` is empty, ``an_element()`` should raise the exception
``EmptySetError``.
This default implementation calls ``_an_element_()`` and cache the
result. Any parent should implement either ``an_element()`` or
``_an_element_()``.
sage: C = EnumeratedSets().parent_class
sage: C._an_element_?
Type: CachedMethodCaller
Base Class: <class 'sage.misc.cachefunc.CachedMethodCaller'>
String Form: Cached version of <function _an_element_from_iterator
at 0x2a93de8>
Namespace: Interactive
File:
/opt/sage/local/lib/python2.6/site-packages/sage/misc/cachefunc.py
Definition: C._an_element_(self, *args, **kwds)
Docstring:
An element in ``self``.
``self.an_element()`` returns a particular element of the set
``self``. This is a generic implementation from the category
``EnumeratedSets()`` which can be used when the method ``__iter__``
is provided.
Cheers,
Nicolas
--
Nicolas M. Thiéry "Isil" <nthi...@users.sf.net>
http://Nicolas.Thiery.name/
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