#9556: Dynamic attributes for symbolic expressions
---------------------------+------------------------------------------------
Reporter: SimonKing | Owner: segfaulting doctests
Type: enhancement | Status: new
Priority: major | Milestone: sage-5.0
Component: symbolics | Keywords: symbolic expression dynamic attribute
Author: | Upstream: N/A
Reviewer: | Merged:
Work_issues: |
---------------------------+------------------------------------------------
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.
'''__Example__'''
{{{
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
... def some_function_name(self, *args):
... return len(args)
...
sage: ex_func = ExampleBuiltin()
sage: ex_func
ex_func
}}}
We obtain a symbolic expression by calling {{{ex_func}}}:
{{{
sage: e = ex_func(x,x+1, x+2)
sage: type(e)
<type 'sage.symbolic.expression.Expression'>
}}}
We add a callable and a non-callable attribute to {{{ex_func}}}:
{{{
sage: def some_function(slf, *L): print slf,'called with',L
...
sage: ex_func.foo_bar = some_function
sage: ex_func.bar_foo = 4
}}}
Now, both the new method and the callable attribute {{{foo_bar}}} of
{{{ex_func}}} are available from {{{e}}}, but not the non-callable:
{{{
sage: e.some_function_name()
3
sage: e.foo_bar()
ex_func called with (x, x + 1, x + 2)
sage: e.bar_foo
Traceback (most recent call last):
...
AttributeError: <type 'sage.symbolic.expression.Expression'> has no
attribute 'bar_foo'
}}}
Tab completion and introspection work:
{{{
sage: 'foo_bar' in dir(e) # indirect doctest
True
sage: 'some_function_name' in dir(e)
True
sage: 'bar_foo' in dir(e)
False
sage: import sagenb.misc.support as s
sage: s.completions('e.some', globals(), system='python')
['e.some_function_name']
}}}
'''__Problems__'''
When I ran {{{sage -testall}}}, several doctests segfaulted:
{{{
sage -t -verbose "devel/sage/sage/functions/hyperbolic.py"
sage -t -verbose "devel/sage/sage/games/hexad.py"
sage -t -verbose "devel/sage/sage/matrix/tests.py"
sage -t -verbose "devel/sage/sage/misc/sage_eval.py"
sage -t -verbose "devel/sage/sage/plot/animate.py"
sage -t -verbose
"devel/sage/sage/quadratic_forms/quadratic_form__mass__Conway_Sloane_masses.py"
sage -t -verbose
"devel/sage/sage/rings/polynomial/polynomial_element.pyx"
}}}
I tried (using {{{sage -t -verbose}}}) to find out what exactly fails.
When I ran some of these failing examples in an interactive session, no
segfault occured. So, is there a nasty side effect?
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/9556>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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