Opened 5 years ago
Last modified 5 years ago
#17412 needs_info enhancement
improve documentation of 'solve()'
Reported by: | jakobkroeker | Owned by: | |
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Priority: | minor | Milestone: | sage-6.5 |
Component: | documentation | Keywords: | |
Cc: | Merged in: | ||
Authors: | Reviewers: | ||
Report Upstream: | N/A | Work issues: | |
Branch: | u/jakobkroeker/ticket/17412 (Commits) | Commit: | 2d7574794ae840b48a0f8841a8978157066982db |
Dependencies: | Stopgaps: |
Description
Even if it is expectable that in some cases solve() may not return all solutions, it should be explicitly pointed out; especially it should be stated that an empty list does not necessarily imply there are no solutions.
See also the discussion at https://groups.google.com/d/msg/sage-support/cg7QYw_1ncg/VKdH3CX4qYsJ
Example from that thread:
solve(5^( x -1) == (1/25)^(2*x), x) # [] solve(5^( x -1) == (1/25)^(2*x), x,to_poly_solve=True) #[x == (2*I*pi*z41 + log(5))/log(3125)]
Change History (5)
comment:1 Changed 5 years ago by
- Branch set to u/jakobkroeker/ticket/17412
- Created changed from 11/28/14 09:59:03 to 11/28/14 09:59:03
- Modified changed from 11/28/14 09:59:03 to 11/28/14 09:59:03
comment:2 Changed 5 years ago by
- Commit set to 2d7574794ae840b48a0f8841a8978157066982db
- Status changed from new to needs_info
comment:3 follow-up: ↓ 4 Changed 5 years ago by
I think you should also give an explicit example in the doc. However, the one you provide does not work for me (on 6.5.beta0):
sage: solve(5^( x -1) == (1/25)^(2*x), x) ... NotImplementedError: non-integral exponents not supported
comment:4 in reply to: ↑ 3 Changed 5 years ago by
Replying to tmonteil:
I think you should also give an explicit example in the doc. However, the one you provide does not work for me (on 6.5.beta0):
sage: solve(5^( x -1) == (1/25)^(2*x), x) ... NotImplementedError: non-integral exponents not supported
Returns empty list on 6.5beta1. Is x
already initialized?
comment:5 Changed 5 years ago by
Uh my bad, i was using the wrong sage console where i used polynomials before. Sorry for the noise.
That said, adding an example showing explicitly the problem (e.g. that particular example, since it works) could be good to make things explicit. The existing example are somehow too optimistic, and we should point what does not work as well.
What is about
may they also fail in some cases to return all solutions? Which other routines need an explicit statement, that an empty result does not imply that there are no solutions?
New commits:
explicitly state that solve may not obtain all existing solutions and that an empty result does not imply there are no solutions