[GiNaC-devel] [BUG] clifford::op() versus tensor::replace_contr_index

[Sheplyakov Alexei]

Hello, Vladimir!

On Wed, Oct 18, 2006 at 03:55:35PM +0100, Vladimir Kisil wrote:
> 	Your exam works smoothly on my computer with CVS GiNaC, expression e
>   is evaluated to gamma~mu, is it correct?
Have you applied my patch to ex.h?

>     ASh> 2) In general, is it OK for class derived from indexed return
>     ASh>    something which is *not* idx (or derived from it) via op()?
> 
> 	One of the reasons why clifford class returns its metric among its
>   ops, I think, because this is required by the subs() method to make symbolic
>   substitution in the metric as well.

Actually, I think this is perfectly sensible, not only for subs()' sake
(one could provide custom implementation of subs). The point of a derived
class is to store some additional data. One might want to make that
data availiable via op(). However, some code in GiNaC seems to make
different assumption (BTW, I hate such *implicit* assumptions).

What about the following patch: 

tensor::replace_contr_index: ignore all non-idx subexpressions.

Classes derived from indexed could make their additional data
members avialable via op(). Ignore such non-idx subexperssions
when performing contractions.

---
 ginac/tensor.cpp |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/ginac/tensor.cpp b/ginac/tensor.cpp
index c215237..25935f4 100644
--- a/ginac/tensor.cpp
+++ b/ginac/tensor.cpp
@@ -395,6 +395,8 @@ bool tensor::replace_contr_index(exvecto
 again:
 	if (self_idx->is_symbolic()) {
 		for (size_t i=1; i<other->nops(); i++) {
+			if (! is_a<idx>(other->op(i)))
+				continue;
 			const idx &other_idx = ex_to<idx>(other->op(i));
 			if (is_dummy_pair(*self_idx, other_idx)) {
 
-- 
1.4.2.3

Best regards,
 Alexei.

-- 
All science is either physics or stamp collecting.

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