Function: indices (<expr>) Returns a list of two elements. The first is a list of the free indices in <expr> (those that occur only once). The second is the list of the dummy indices in <expr> (those that occur exactly twice) as the following example demonstrates.
(%i1) load(itensor); (%o1) /share/tensor/itensor.lisp (%i2) ishow(a([i,j],[k,l],m,n)*b([k,o],[j,m,p],q,r))$ k l j m p (%t2) a b i j,m n k o,q r (%i3) indices(%); (%o3) [[l, p, i, n, o, q, r], [k, j, m]]
A tensor product containing the same index more than twice is syntactically illegal.
indices attempts to deal with these expressions in a reasonable manner; however, when it is called to operate upon such an illegal expression, its behavior should be considered undefined.
There are also some inexact matches for
?? indices to see them.
(%o1) true (%i2)