Putting == between two symbol expressions creates a symbolic equation,
not a test for equality. There is there fore a difference between
these:
sage: 3 == 3
True
sage: x == x
x == x
This behaviour of == is (I think) unique to the symbolic ring in Sage.
You can test for equality like this:
sage: dSv-dSvq
0
sage: (dSv-dSvq).is_zero()
True
though in more complicated examples the expessions might have to be
simplified manually.
In general in computer algebra, simplifying an expression which
simplifies to 0 is easier than trying to find two simplifications of
two expressions which appear to be the same.
I'm sure there are computer algebra experts reading this who can
explain it better.
John
2008/9/2 Stan Schymanski <[EMAIL PROTECTED]>:
>
> Dear all,
>
> I must be doing something wrong here, but I don't know what. I'm sure
> someone will see it straight away:
>
> ----------------------------------------------------------------------
> | SAGE Version 3.1.1, Release Date: 2008-08-17 |
> | Type notebook() for the GUI, and license() for information. |
> ----------------------------------------------------------------------
>
> sage: var('myuv myub q qvb qbv')
> (myuv, myub, q, qvb, qbv)
> sage: dSv=myuv*qvb - myuv*qbv
> sage: dSvq=myuv*qvb - myuv*qbv
> sage: dsage: dSv-dSvq
> myuv*qvb - myuv*qbv == myuv*qvb - myuv*qbv
>
> Why does SAGE not return 'true'?
>
> Just pointing me to the right page in the docu would help, too! Thanks
> already.
>
> Stan
> >
>
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