What I'm doing in this case is writing simple functions, say y = log(2*x)/2 - 3 and then computing their inverse through a function I made myself. The usefulness in having domains is that when you compute an inverse of a function, the domain of the inverse is the range of the original. Likewise, the range of the inverse is the domain of the original.
Since it's for my own purposes I really could represent it with nested lists/tuples, using booleans to include a value or not: [[(-sympy.oo, False), (-1, True)], [(0, False), (sympy.oo, True)]] which represents (-inf, -1] U (0, inf) which would work fine for my purposes. However I'm pretty sure with what I plan to do I'm going to be using domains a fair bit more in the future so if I have something that is going to work with what SymPy has planned then it may help. On 24 July 2013 21:34, Stefan Krastanov <[email protected]> wrote: > It depends what exactly you want to do. > > If you need it just for typography purposes (e.g. writing something in > IPython notebook and wanting to print the expression) you are using sympy > incorrectly. SymPy is not a typography library. (if you insists there are > hacks to do it) > > On the other hand quite frequently you need this for meaningful > mathematics. > > - if you want to work on polynomials and do certain operations (finding > roots, etc) over a given field, you do this by specifying the field during > the creation of the polynomial. > > - there is some work in progress to be able to do the same for matrices, > but it is not ready. > > - in general, there is the assumption module. It is a bit of a mess, > because we have an old and a new assumption module and we try to move to > the new one. If all that you want is for abs(x) to automatically return x > (or something similar) it suffices to define x as `x=Symbol('x', > positive=True)`. There are a few other handles like `real` and `integer`. > > - if you need something more general or more fancy, we may have it in some > (possibly unfinished, mostly unused) form, but it goes deeper in SymPy so a > more precise question will help us give you a more precise answer. > > > On 24 July 2013 13:10, Ben Lucato <[email protected]> wrote: > >> We can represent domains on paper quite easily - for instance we can >> write x < 0, or alternatively x (epsilon symbol) R-, or even x (epsilon >> symbol) (-infinity, 0) >> >> I looked around but couldn't really find that - is there a canonical way >> to be writing domains in SymPy? >> >> -- >> 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 a topic in the > Google Groups "sympy" group. > To unsubscribe from this topic, visit > https://groups.google.com/d/topic/sympy/vMa2TEbdb-k/unsubscribe. > To unsubscribe from this group and all its topics, 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. > > > -- Ben Lucato ---------------------------------------------------------------------------------- Phone: +61 400 159 632 | Email: [email protected] -- 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.
