On Sat, Apr 4, 2009 at 9:37 AM, Freddie Witherden <fred...@witherden.org> wrote:
> Hi all,
>
> I am wondering if it is possible to change the real=True|False property of
> the symbols used by sympify/S created when parsing an expression.
>
> E.g., S('sqrt(x^2)'), how can I then specify that x is real? While I can
> access the Symbol's using .atoms(Symbol) I can not work out how to modify
> their properties.
>
> What is the best way of going about this?
You can give your symbols to sympify, e.g.:
In [2]: sympify("sqrt(x**2)", {"x": Symbol("x", positive=True)})
Out[2]: x
In [3]: sympify("sqrt(x**2)", {"x": Symbol("x", negative=True)})
Out[3]: -x
But after our new assumption system, this will not be needed anymore.
Ondrej
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