#20312: parent of argument lost with Functions
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Reporter: rws | Owner:
Type: defect | Status: new
Priority: major | Milestone: sage-7.2
Component: symbolics | Resolution:
Keywords: | Merged in:
Authors: Ralf Stephan | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
u/rws/parent_of_argument_lost_with_functions|
eb5bf9367e1f781b6a5e649f4be6fe0fa4da2c39
Dependencies: | Stopgaps:
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Changes (by {'newvalue': u'Ralf Stephan', 'oldvalue': ''}):
* commit: => eb5bf9367e1f781b6a5e649f4be6fe0fa4da2c39
* author: => Ralf Stephan
Comment:
It looks like the first version here can handle the binomial example of
#20060 as well as the symbolic poly functions. It works by adding a field
`_preserved_arg` to every `BuiltinFunction` that is set on function
creation and says which of the function arguments is the one where we try
to preserve the arg's parent. Then `Expression.polynomial()` is used to
convert back in case of polynomial rings. Also, by not setting a default
`preserved_arg` the functionality is limited to the cases where the
developer has given this parameter in the function init call.
This does not work however with the title example because there the
functions are nested. Since it seems we cannot decide where in a nested
expression the specific element is whose parent we want to preserve I tend
to exclude the nested case.
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New commits:
||[http://git.sagemath.org/sage.git/commit/?id=eb5bf9367e1f781b6a5e649f4be6fe0fa4da2c39
eb5bf93]||{{{20312: preserving function arg parent, first version}}}||
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Ticket URL: <http://trac.sagemath.org/ticket/20312#comment:6>
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