Recent work on sets provides mechanisms to handle this problem In [2]: from sympy.sets.setexpr import SetExpr
In [3]: epsilon = SetExpr(Interval(0, oo)) In [4]: beta = SetExpr(Interval(0, oo)) In [5]: exp(epsilon * beta) - 1 Out[5]: [0, ∞) This is from my setexpr development branch https://github.com/sympy/sympy/pull/2721 . It is not yet in master Harsh has also done some work on this issue. In particular https://github.com/sympy/sympy/pull/2682 On Fri, Feb 7, 2014 at 7:50 PM, Harsh Gupta <[email protected]> wrote: > Thanks for posting this on the mailing list. > > > There's also a bug in the new `solve_univariate_inequalities` > > ``` > > In [2]: x = Symbol('x', positive=True) > > > In [3]: y = Symbol('y') > > > In [4]: solve_univariate_inequality(exp(x) > 1, x) > > Out[4]: False > > > In [5]: solve_univariate_inequality(exp(y) > 1, y) > > Out[5]: y > 0 > ``` > > This was caused by me by not taking care of the assumptions on the > variables. I'll fix it asap. > > On 8 February 2014 07:28, Aaron Meurer <[email protected]> wrote: > > No, unfortunately, non-trivial relational assumptions like this are > > largely not implemented. As you may or may not know, the assumptions > > system in SymPy is currently in a bit of a mess. There are two > > assumptions systems, the "old" one, which is the one you used, and the > > "new" one, which uses ask() and Q. > > > > Neither can handle this, or really any kind of non-trivial > > Add.is_positive type assumption. It's not even clear to me at the > > moment how one would go about implementing such things. > > > > Aaron Meurer > > > > On Fri, Feb 7, 2014 at 11:47 AM, Patrick O'Neill <[email protected]> wrote: > >> Howdy folks, > >> > >> I'm a very new to sympy, and am stumped by the following error. > Considering > >> the following code snippet: > >> > >> from sympy import * > >> print sympy.__version__ > >> #'0.7.4.1-git' > >> epsilon,beta = var("epsilon,beta",positive=True) > >> (exp(epsilon*beta) - 1).is_positive # is None > >> > >> Sympy knows that beta and epsilon are positive, but seems not to know > that > >> the exponential function takes positive quantities to quantities greater > >> than one. Is there a workaround for this issue, or is there something > >> fundamental to sympy's internals that makes this sort of deduction > >> impossible? > >> > >> I checked the mailing list, stack overflow and the issue tracker, and > didn't > >> see anything pertaining to this question, but I admit I might not know > what > >> I'm looking for. > >> > >> Thanks in advance! > >> > >> Cheers, > >> Pat. > >> > >> > >> On Fri, Feb 7, 2014 at 12:45 PM, Patrick O'Neill <[email protected]> wrote: > >>> > >>> Howdy folks, > >>> > >>> I'm a very new to sympy, and am stumped by the following error. > >>> Considering the following code snippet: > >>> > >>> from sympy import * > >>> print sympy.__version__ > >>> #'0.7.4.1-git' > >>> epsilon,beta = var("epsilon,beta",positive=True) > >>> (exp(epsilon*beta) - 1).is_positive # is None > >>> > >>> Sympy knows that beta and epsilon are positive, but seems not to know > that > >>> the exponential function takes positive quantities to quantities > greater > >>> than one. Is there a workaround for this issue, or is there something > >>> fundamental to sympy's internals that makes this sort of deduction > >>> impossible? > >>> > >>> I checked the mailing list, stack overflow and the issue tracker, and > >>> didn't see anything pertaining to this question, but I admit I might > not > >>> know what I'm looking for. > >>> > >>> Thanks in advance! > >>> > >>> Cheers, > >>> Pat. > >> > >> > >> -- > >> You received this message because you are subscribed to the Google > Groups > >> "sympy" group. > >> To unsubscribe from this group and stop receiving emails from it, send > an > >> email to [email protected]. > >> To post to this group, send email to [email protected]. > >> Visit this group at http://groups.google.com/group/sympy. > >> For more options, visit https://groups.google.com/groups/opt_out. > > > > -- > > You received this message because you are subscribed to the Google > Groups "sympy" group. > > To unsubscribe from this group and stop receiving emails from it, send > an email to [email protected]. > > To post to this group, send email to [email protected]. > > Visit this group at http://groups.google.com/group/sympy. > > For more options, visit https://groups.google.com/groups/opt_out. > > > > -- > Harsh > > -- > You received this message because you are subscribed to the Google Groups > "sympy" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To post to this group, send email to [email protected]. > Visit this group at http://groups.google.com/group/sympy. > For more options, visit https://groups.google.com/groups/opt_out. > -- You received this message because you are subscribed to the Google Groups "sympy" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/sympy. For more options, visit https://groups.google.com/groups/opt_out.
