Opened 10 years ago
Last modified 4 years ago
#9556 closed enhancement
Dynamic attributes for symbolic expressions — at Version 10
Reported by: | SimonKing | Owned by: | |
---|---|---|---|
Priority: | major | Milestone: | sage-5.11 |
Component: | symbolics | Keywords: | symbolic expression dynamic attribute sd48 |
Cc: | burcin, kcrisman, vbraun, eviatarbach | Merged in: | |
Authors: | Burcin Erocal, Simon King, Mike Hansen | Reviewers: | |
Report Upstream: | N/A | Work issues: | segfaulting doctests |
Branch: | Commit: | ||
Dependencies: | Stopgaps: |
Description (last modified by )
Let e
be a symbolic expression. It may happen that e.operator()
has a certain callable attribute, say, foo
, that is not a method of Function
. In this situation, one would like to use e.foo()
, which is supposed to return e.operator().foo(*e.operands())
- apparently this is useful for working with hypergeometric functions (#2516).
Example
sage: from sage.symbolic.function import BuiltinFunction sage: class TFunc(BuiltinFunction): ....: def __init__(self): ....: BuiltinFunction.__init__(self, 'tfunc', nargs=1) ....: ....: class EvaluationMethods: ....: def argp1(self, x): ....: ''' ....: Some documentation about a bogus function. ....: ''' ....: return x+1 ....: ....: @property ....: def foo(self): ....: return 5 ....: sage: tfunc = TFunc() sage: e = tfunc(x); e tfunc(x) sage: type(e) <class '__main__.Expression_with_dynamic_methods'> sage: e.argp1() x + 1 sage: e.foo 5 sage: x.argp1() Traceback (most recent call last): ... AttributeError: 'sage.symbolic.expression.Expression' object has no attribute 'argp1' sage: t = (e + 1).op[0]; t tfunc(x) sage: t tfunc(x) sage: type(t) <class '__main__.Expression_with_dynamic_methods'> sage: t.argp1() x + 1 sage: import sagenb.misc.support as s sage: s.completions('t.argp', globals(), system='python') ['t.argp1'] sage: t.argp1.__doc__.strip() 'Some documentation about a bogus function.'
Change History (12)
Changed 10 years ago by
comment:1 Changed 10 years ago by
- Owner changed from segfaulting doctests to (none)
comment:2 Changed 10 years ago by
- Cc burcin added
- Status changed from new to needs_work
- Work issues set to segfaulting doctests
Sorry, accidentally I inserted the work issue "segfaulting doctests" into the owner field.
It would be nice to have a segfaulting example that works interactively.
comment:3 follow-up: ↓ 7 Changed 10 years ago by
What is the typical use case for this? Are you just looking for a place to put the functions for evaluated function? Or do you really want the function to appear on both the function and its evaluations? It seems like the first case is what you really want.
We currently have all of the machinery to do this and it's used for the category code. Using this, you would have something like the following:
class ExampleBuiltin(BuiltinFunction): def __init__(self): BuiltinFunction.__init__(self, 'ex_func', nargs=0) #arbitrary no of args class EvaluationMethods: def some_function_name(self): return len(self.operands())
comment:4 follow-up: ↓ 8 Changed 10 years ago by
I did a little mockup using this idea.
sage: from sage.symbolic.function import BuiltinFunction sage: class ExampleBuiltin(BuiltinFunction): ....: def __init__(self): ....: BuiltinFunction.__init__(self, 'ex_func', nargs=0) #arbitrary no of args ....: class EvaluationMethods: ....: def some_function_name(self): ....: return len(self.operands()) ....: sage: ex_func = ExampleBuiltin() sage: f = ex_func(x, x+1, x+2) sage: f.some_function_name() 3 sage: abs(f) abs(ex_func(x, x + 1, x + 2))
Changed 10 years ago by
comment:5 Changed 10 years ago by
Note that pickling also works:
sage: loads(dumps(ceil(x))).foo_bar() 4
One issue is that in order to get the dynamic features, you have to go through the call method of the function. Thus, you'd have to change Expression.abs
return new_Expression_from_GEx(self._parent, g_abs(self._gobj))
to return the dynamic class version. Similarly, unpickling old objects will just return an Expression object.
comment:6 Changed 10 years ago by
Also, all tests pass with this.
comment:7 in reply to: ↑ 3 Changed 10 years ago by
Replying to mhansen:
What is the typical use case for this? Are you just looking for a place to put the functions for evaluated function? Or do you really want the function to appear on both the function and its evaluations?
Sorry that I was absent for some hours.
Unfortunately I don't know what the real use case is. It was a suggestion of Burcin, and I merely tried to implement what he suggested.
Burcin, could you comment on what is really expected?
comment:8 in reply to: ↑ 4 Changed 10 years ago by
Replying to mhansen:
I did a little mockup using this idea.
sage: f = ex_func(x, x+1, x+2) sage: f.some_function_name() 3 sage: abs(f) abs(ex_func(x, x + 1, x + 2))
... which seems like the correct answer to me. So, the fact that ex_func
has an _abs_
method helps to get the right answer for f
.
comment:9 Changed 9 years ago by
- Cc kcrisman added
comment:10 Changed 7 years ago by
- Cc vbraun added
- Description modified (diff)
- Status changed from needs_work to needs_review
I uploaded a new patch that uses Mike's dynamic class idea, but applies to all code paths that might generate symbolic expressions with minimal speed penalty. Please review.
Patchbot, apply only trac_9556-dynamic_class_everywhere.patch.
The patch implements dynamic attributes, but some doctests segfault