#12978: conditionally_defined decorator for methods and other attributes
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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: #15056 | Stopgaps:
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Comment (by SimonKing):
With the latest version of #15056 and the patch that I have just attached,
one can do (that's currently the only doctest):
{{{
sage: from sage.misc.conditionally_defined import
conditionally_defined
sage: class A(object):
....: @cached_method
....: def method1(self, x):
....: print "calling cached method1"
....: return -x
....: def method2(self, x):
....: print "calling method2"
....: return 2*x
sage: class B(A):
....: @conditionally_defined(lambda x: x.con>0)
....: def method1(self, x):
....: print "calling uncached method1"
....: return x^2
....: @cached_method
....: @conditionally_defined(lambda x: x.con<0)
....: def method2(self, x):
....: print "calling alternative method2"
....: return 2+x
sage: x = B()
sage: y = B()
sage: x.con = 1
sage: y.con = -1
}}}
The method `method1` of the two instances `x` or `y` is either a usual
method,
or a cached method, depending on the value of the attribute `.con`:
{{{
sage: x.method1
<bound method B.method1 of <__main__.B object at ...>>
sage: y.method1
Cached version of <bound method B.method1 of <__main__.B object at
...>>
sage: x.method1(3)
calling uncached method1
9
sage: x.method1(3)
calling uncached method1
9
sage: y.method1(3)
calling cached method1
-3
sage: y.method1(3) is y.method1(3)
True
}}}
The method `method2` is cached, but the underlying function of the cached
method is conditionally defined::
{{{
sage: x.method2
Cached version of <bound method B.method2 of <__main__.B object at
...>>
sage: y.method2
Cached version of <bound method B.method2 of <__main__.B object at
...>>
sage: x.method2(3)
calling method2
6
sage: x.method2(3) is x.method2(3)
True
sage: y.method2(3)
calling alternative method2
5
sage: y.method2(3) is y.method2(3)
True
}}}
Do you agree that this seems useful?
--
Ticket URL: <http://trac.sagemath.org/ticket/12978#comment:17>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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