By the way, if you only care printing, I think it should be possible to configure the printer to do what you want. Then you just have to add one line that configures the printer to the top of your doctests (if it's a Sphinx file, you just need one line at the top of the file).
Aaron Meurer On Sat, Jul 23, 2011 at 6:23 PM, Matthew Brett <matthew.br...@gmail.com> wrote: > Hi, > > On Sun, Jul 24, 2011 at 1:06 AM, Aaron Meurer <asmeu...@gmail.com> wrote: >> On Sat, Jul 23, 2011 at 5:59 PM, Matthew Brett <matthew.br...@gmail.com> >> wrote: >>> Hi, >>> >>> On Sun, Jul 24, 2011 at 12:36 AM, Aaron Meurer <asmeu...@gmail.com> wrote: >>>> On Sat, Jul 23, 2011 at 5:28 PM, Matthew Brett <matthew.br...@gmail.com> >>>> wrote: >>>>> Hi, >>>>> >>>>> On Sun, Jul 24, 2011 at 12:23 AM, Aaron Meurer <asmeu...@gmail.com> wrote: >>>>>> Note that Float(1) is not the same as Float(1.0). Fredrik or someone >>>>>> else would have to explain the details, but I think the reasoning >>>>>> behind Float(int) => Integer is something related to precision. >>>>> >>>>> Right, sorry, I should have added that: >>>>> >>>>> sympy.Float(1.0) == sympy.numbers.One() >>>> >>>> ==, yes, but is, no. >>> >>> Surely == is the relevant operator? >>> >>>> In [2]: Float(1.0) is S.One >>>> Out[2]: False >>>> >>>> In [3]: Float(1.0) == S.One >>>> Out[3]: True >>>> >>>> == works because of some type casting. You also get, for example: >>>> >>>> In [4]: 0.5 == Rational(1, 2) >>>> Out[4]: True >>>> >>>>> >>>>>> Also, as the commit message notes, there is the following >>>>>> inconsistency in 0.6.7: >>>>>> >>>>>> In [1]: -1.0*x >>>>>> Out[1]: -1.0⋅x >>>>>> >>>>>> In [2]: 1.0*x >>>>>> Out[2]: x >>>>> >>>>> To me, that inconsistency is a benefit. Is there some disbenefit? >>>>> I'm asking honestly. For me it is just a question of reduced >>>>> readability in doctests and examples. >>>>> >>>>> Cheers, >>>>> >>>>> Matthew >>>>> >>>> >>>> Yes, I think there is a disbenefit, because you loose the precision >>>> information in 1.0 when you convert it to S.One. >>>> >>>> This will happen when you use Floats. They are assumed to be close to >>>> (up to their precision), but not necessarily equal to the numbers the >>>> represent. So with the default precision of 15 or something like >>>> that, 1.0 is really 1 +- 1e-15. If you really want exact numbers >>>> (i.e., rationals), you should use them. Otherwise, SymPy assumes that >>>> Floats are not exact, and treats them as such. >>> >>> I believe that the integers up to around 2^52 are exactly >>> representable in 64 bit doubles: >>> >>> http://stackoverflow.com/questions/440204/does-floor-return-something-thats-exactly-representable >>> >>> so 1.0 will always be exactly representable in float. Indeed, it >>> seems to me confusing to imply that I don't have exactly 1.0 by >>> retaining it. >>> >>>> Others, if any of this is not true, please correct me. >>>> >>>> By the way, if you want to convert from floats to rationals, you can >>>> use nsimplify: >>>> >>>> In [14]: nsimplify(1.0*x, rational=True) >>>> Out[14]: x >>> >>> Right - but it seems ugly and unfortunate to add that to the doctests, >>> and examples, especially where we have matrices where we have to >>> iterate over all the values looking for these guys. >>> >>> Well - sorry - I'll consider my peanut thrown and missed :) >>> >>> Cheers, >>> >>> Matthew >>> >> >> Well, maybe others could chip in here. > > While I am at it, surely this is surprising?: > > In [44]: simplify(x * 1.0) > Out[44]: 1.0*x > > and identity under addition doesn't have the same feature: > > In [42]: x + 0.0 > Out[42]: x > > What do Mathematica etc do in this case? > > See you, > > Matthew > > -- > You received this message because you are subscribed to the Google Groups > "sympy" group. > To post to this group, send email to sympy@googlegroups.com. > To unsubscribe from this group, send email to > sympy+unsubscr...@googlegroups.com. > For more options, visit this group at > http://groups.google.com/group/sympy?hl=en. > > -- You received this message because you are subscribed to the Google Groups "sympy" group. To post to this group, send email to sympy@googlegroups.com. To unsubscribe from this group, send email to sympy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sympy?hl=en.
