Opened 5 years ago
Closed 4 years ago
#20179 closed enhancement (fixed)
add a free_variables() method?
| Reported by: | wonder | Owned by: | |
|---|---|---|---|
| Priority: | major | Milestone: | sage-8.0 |
| Component: | symbolics | Keywords: | |
| Cc: | charpent | Merged in: | |
| Authors: | Ralf Stephan | Reviewers: | Travis Scrimshaw |
| Report Upstream: | N/A | Work issues: | |
| Branch: | 5b93a06 (Commits) | Commit: | 5b93a067769f0a49267a010401366de43c0cfdb0 |
| Dependencies: | #22844, #23134 | Stopgaps: |
Description
It can be useful to query the free variables in an expression. SR's variables() and arguments() return all variables in an expression, whether free or bound. For example:
sage: var('y')
y
sage: function('f')
f
sage: e = limit( f(x,y), x=0 )
sage: e
limit(f(x, y), x, 0)
sage: e.variables()
(x, y)
I would like to have a free_variables() method that returns only y in this case. Is there a recommended way to get this information from an expression?
Change History (13)
comment:1 Changed 5 years ago by
comment:2 Changed 5 years ago by
The free variables in an expression are all its variables excluding any that are bound, for example, in limits, sums, products, or integrals.
See for example https://en.wikipedia.org/wiki/Free_variables_and_bound_variables for a definition.
comment:3 Changed 4 years ago by
Implemented in pynac git master. Will be in the upcoming Pynac-0.7.6.
comment:4 Changed 4 years ago by
- Branch set to u/rws/add_a_free_variables___method_
comment:5 Changed 4 years ago by
- Commit set to 5b93a067769f0a49267a010401366de43c0cfdb0
- Milestone changed from sage-7.1 to sage-8.0
This is not read for review because it doesn't work as expected but at least the interface is there now.
New commits:
| 3c848da | 22838: pkg version/checksum
|
| d89e6d0 | 22838: remove unnecessary patch
|
| 4a30119 | 22838: interface change
|
| 7d3fd60 | 22838: doctest adaptation to ticket 10070
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| 5b93a06 | 20179: interface to Pynac's ex::free_symbols()
|
comment:6 Changed 4 years ago by
- Dependencies set to #22844
comment:7 Changed 4 years ago by
- Cc charpent added
comment:8 Changed 4 years ago by
- Dependencies changed from #22844 to #22844, pynac-0.7.8
The problems seem resolved, now that there is a symbolic limit, and code in Pynac master that recognizes it and its bound symbols.
comment:9 Changed 4 years ago by
- Dependencies changed from #22844, pynac-0.7.8 to #22844, #23134
comment:10 Changed 4 years ago by
- Reviewers set to Travis Scrimshaw
Is this ready for review? If so, then you can set it to positive review on my behalf.
comment:11 Changed 4 years ago by
- Status changed from new to needs_review
Yes, I usually wait until the merge of the Pynac upgrade because not all reviewers want to go through the hassle of manual Pynac install. Thanks.
comment:12 Changed 4 years ago by
- Status changed from needs_review to positive_review
comment:13 Changed 4 years ago by
- Branch changed from u/rws/add_a_free_variables___method_ to 5b93a067769f0a49267a010401366de43c0cfdb0
- Resolution set to fixed
- Status changed from positive_review to closed
These are practically all variables, minus the one(s) the limit is over?