Hi Jeremy,
thanks for sharing your link and thanks for compiling the documentation. And
indeed it helped, with the information I could easily fix it:
rd@h370:~/tmp.nobackup$ cat test-sympy.py
import sympy
x, y, z = sympy.symbols('x y z')
sympy.init_printing(use_unicode=True)
print(sympy.solvers.inequalities.reduce_rational_inequalities([[x + 2 > 0]],
x))
print(sympy.solvers.inequalities.reduce_rational_inequalities([[x + 2 > 0,x <
5]], x))
rd@h370:~/tmp.nobackup$ python3 test-sympy.py
(-2 < x) & (x < oo)
(-2 < x) & (x < 5)
rd@h370:~/tmp.nobackup$
I read through your page and posted some feedback at
https://github.com/sympy/sympy/pull/23768
My real problem is somewhat more complex though:
I want to find out if
f_vec+a*x_vec+b*y_vec+n*s_vec=sh_vec+c*xsh_vec+d*ysh_vec
has a solution with
0<=a,b,c,d<=1
All quantities with _vec are 3 dimensional vectors. I want to to find out if
for a given set of vectors a solution exists or not.
Extending my testcase in this direction does not work though:
rd@h370:~/tmp.nobackup$ cat test-sympy.py
import sympy
x, y, z = sympy.symbols('x y z')
sympy.init_printing(use_unicode=True)
print(sympy.solvers.inequalities.reduce_rational_inequalities([[x + 2 > 0]],
x))
print(sympy.solvers.inequalities.reduce_rational_inequalities([[x*5 + y*2 =
10,x <= 1, x >= 0, y <= 1, y >= 0]], x))
rd@h370:~/tmp.nobackup$ python3 test-sympy.py
File "/home/rd/tmp.nobackup/test-sympy.py", line 9
print(sympy.solvers.inequalities.reduce_rational_inequalities([[x*5 + y*2
= 10,x <= 1, x >= 0, y <= 1, y >= 0]], x))
^
SyntaxError: invalid syntax
rd@h370:~/tmp.nobackup$
I suspect that reduce_rational_inequalities is the wrong approach here, but
what would the the right functions to use?
Any hint is welcome :-)
Many thanks
Rainer
PS: Also thanks for hint towards less-verbose function calls. I typically
write it verbose, since I am not writing Python code too frequently, and for
me the verbose version is something like a documentation, since I see where
the functions come from.
Am Samstag, 6. August 2022, 17:19:45 CEST schrieb Jeremy Monat:
> Hi Ranier,
>
> Here's a way to do it:
> >>> import sympy
> >>> x, y, z = sympy.symbols('x y z')
> >>> sympy.solvers.inequalities.reduce_inequalities([x + 2 > 0, x < 5], x)
>
> (-2 < x) & (x < 5)
>
> reduce_inequalities is the top-level inequality reducer, which will call
> other lower-level functions (such as reduce_rational_inequalities) as
> needed. reduce_inequalities takes a simple list, rather than a nested list,
> of inequalities.
>
> I'm actually drafting a guide page on this topic now; glad to know it's of
> interest! You can access the draft
> <https://output.circle-artifacts.com/output/job/a1f8297d-6be8-4627-9f47-a969
> 709f9293/artifacts/0/doc/_build/html/guides/solving/solve-system-of-inequali
> ties-algebraically.html>, and I'd appreciate any feedback (either here or on
> the pull request <https://github.com/sympy/sympy/pull/23768> on GitHub).
>
> Best,
> Jeremy
>
> P.S. If you like, you can use less-verbose function calls by importing
>
> reduce_inequalities and symbols from SymPy:
> >>> from sympy import reduce_inequalities, symbols
> >>> x, y, z = symbols('x y z')
> >>> reduce_inequalities([x + 2 > 0, x < 5], x)
>
> (-2 < x) & (x < 5)
>
> On Sat, Aug 6, 2022 at 3:31 AM 'Rainer Dorsch' via sympy <
>
> [email protected]> wrote:
> > Hi,
> >
> > I just started with sympy, and try to understand how to tell sympy, what I
> > want. I tried
> > print(sympy.solvers.inequalities.reduce_rational_inequalities([[x + 2 >
> > 0],[x
> > < 5]], x))
> > and expected
> > (-2 < x) & (x < 5)
> > but got
> > (-oo < x) & (x < oo)
> > Can anybody tell how I can tell sympy that x should satisfy both
> > inequalities
> > the same time?
> > For me it seems sympy rather interprets the set of equations rather as an
> > "or"
> > and not an "and"
> >
> > Here is the full example
> >
> > rd@h370:~/tmp.nobackup$ cat test-sympy.py
> > import sympy
> >
> > x, y, z = sympy.symbols('x y z')
> > sympy.init_printing(use_unicode=True)
> >
> > print(sympy.solvers.inequalities.reduce_rational_inequalities([[x + 2 >
> > 0]],
> > x))
> >
> >
> > print(sympy.solvers.inequalities.reduce_rational_inequalities([[x + 2 >
> > 0],[x
> > < 5]], x))
> > rd@h370:~/tmp.nobackup$ python3 test-sympy.py
> > (-2 < x) & (x < oo)
> > (-oo < x) & (x < oo)
> > rd@h370:~/tmp.nobackup$
> >
> >
> > Any hint is welcome.
> >
> > Thanks
> > Rainer
> >
> >
> > --
> > Rainer Dorsch
> > http://bokomoko.de/
> >
> >
> > --
> > You received this message because you are subscribed to the Google Groups
> > "sympy" group.
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> > email to [email protected].
> > To view this discussion on the web visit
> > https://groups.google.com/d/msgid/sympy/4120287.OZXsGyJSKq%40h370.
--
Rainer Dorsch
http://bokomoko.de/
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