Hello,
Suppose that I have an expression such as the one given below:
M = Indexed('M')
var('A B C')
i,j,n = symbols('i j n', integer = True)
expr = A*M(1,2)**n + B*M(-2,1)**n + C*M(-1,-1)**n
Is there a way to iterate through this expression and apply the
following sequence of operations?
(1
On Sep 24, 2010, at 9:20 AM, Nicholas Kinar wrote:
> Hello,
>
> Suppose that I have an expression such as the one given below:
>
> M = Indexed('M')
> var('A B C')
> i,j,n = symbols('i j n', integer = True)
>
> expr = A*M(1,2)**n + B*M(-2,1)**n + C*M(-1,-1)**n
>
> Is there a way to iterate thro
There's no need to iterate through the expression to do this. Just use subs,
i.e., expr.subs({M(1, 2)**n: Symbol('M_1_2_n'), M(-2, 1)**n:
Symbol('M_neg2_1_n'), …})
Of course, if you want to generate the Symbols automatically, that would
require you to be a little more clever.
Yes, I would
On Sep 24, 2010, at 9:43 AM, Nicholas Kinar wrote:
>
>> There's no need to iterate through the expression to do this. Just use
>> subs, i.e., expr.subs({M(1, 2)**n: Symbol('M_1_2_n'), M(-2, 1)**n:
>> Symbol('M_neg2_1_n'), …})
>>
>> Of course, if you want to generate the Symbols automatically
There is (I gave it below :)
Aaron Meurer
Then I think that .subs() could be used to make the substitution.
(2) For every replacement, a list (or similar data structure) is created with
the names of the variables [M_1_2_n, M_neg2_1_n, M_neg1_neg1_n]. The list
contains the names of unique
fr., 24.09.2010 kl. 09.34 -0600, skrev Aaron S. Meurer:
> On Sep 24, 2010, at 9:20 AM, Nicholas Kinar wrote:
>
> > Hello,
> >
> > Suppose that I have an expression such as the one given below:
> >
> > M = Indexed('M')
> > var('A B C')
> > i,j,n = symbols('i j n', integer = True)
> >
> > expr =
Hmm. To me, it seems like ccode() should be able to do this on its own. Maybe
you could submit it as a patch to ccode(). Or maybe it really can and neither
of us know about it. Øyvind (or anyone)?
There is a lot of pending patches that will improve the support for
Indexed in ccode. You ca
fr., 24.09.2010 kl. 10.25 -0600, skrev Nicholas Kinar:
> > Hmm. To me, it seems like ccode() should be able to do this on its own.
> > Maybe you could submit it as a patch to ccode(). Or maybe it really can
> > and neither of us know about it. Øyvind (or anyone)?
> > There is a lot of pending
So it sounds like that is what you want to do. I guess you need to combine the
expr.atoms(IndexedElement) with str() or .args and some regular expression
replacement. Something like '_'.join([str(t) for t in
index.args]).replace('-', 'neg'), where index is a M(1, 2, …) element (again a
ver
