Don't simplify

[Vincent MAILLE]

Hello,

I'm programming a function whitch give the definition set of an
expression (e.g : ln(x+1) => ]-1;+oo[ ). My problem is sympy
simplifies too quick my expression :

print x/x return 1 before I can extract the 1/x operation (and so
return x<>0). How to say sympy not to symplify ?

Thanks.
Vincent

P.S : Perhaps this function already exists ?

[Chris Smith]

On Sun, Dec 18, 2011 at 7:32 PM, Vincent MAILLE <htcv...@gmail.com> wrote:
> Hello,
>
> I'm programming a function whitch give the definition set of an
> expression (e.g : ln(x+1) => ]-1;+oo[ ). My problem is sympy
> simplifies too quick my expression :
>
> print x/x return 1 before I can extract the 1/x operation (and so
> return x<>0). How to say sympy not to symplify ?

Maybe this is what you mean?

>>> xx=Mul(x,1/x,evaluate=0)
>>> log(xx+1)
log(1 + x/x)

[Aaron Meurer]

If http://code.google.com/p/sympy/issues/detail?id=1966 were fixed,
you would be able to just do sympify('x/x', evaluate=False).

By the way, do you know about the Interval class (or more generally,
the Set classes) in SymPy? It doesn't use the same notation as you do
in printing, but this can be easily fixed by modifying the printer if
you dislike it.

Aaron Meurer

[Vincent MAILLE]

Hello. Thanks for your answer.

Issue 1966 would be fine indeed (I clicked +1). Regarding intervals, I use them afterwards to display the definition domain of the function, but first I have to pick out all the problematical values. I've almost finished the code. I'll add it on this list if you're interested in it

Thanks

Vincent

[Christophe BAL]

Hello Voncent,
is it possible to use your code ?

Christophe

2011/12/22 Vincent MAILLE <htcv...@gmail.com>

Vincent

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[Chris Smith]

btw, as far as finding problem values, solve's denoms function might be useful: it sends back all denominators in an expression.

[Vincent MAILLE]

Hi Christophe,

    Yes of course !  I think my code can be very optimized. I'll send you here when it'll be finished (in January I hope)

Vincent

[Christophe BAL]

Thanks for this christmas gift !

C.