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I admit I’m a bit desperate for a solution here, I have defined in Mathematica:

  1. A basis newBasis (built from a function f[c[i],c[j],c[k]]).
  2. A set of rewrite rules reorderIndices and adjRepr to put those f[…] into a canonical form.
  3. A set of “product‐to‐**” rules
matrixProduct := {
  A_[a_][i_, j_] B_[b_][j_, k_] -> A[a] ** B[b][i, k],
  A_[a_] ** B_[b_][i_, j_]  C_[c_][j_, k_] -> 
   A[a] ** B[b] ** C[c][i, k],
  A_[a_] ** B_[b_][j_, i_]  C_[c_][k_, j_] -> 
   C[c] ** A[a] ** B[b][k, i],
  resta___ ** a___[i_, j_] restb___ ** b___[j_, k_] -> 
   resta ** a ** restb ** b[i, k]
  }

When I do

basis = newBasis /. reorderIndices[5] //. adjRepr;
basis = basis //. matrixProduct;
cBasis = complexConjugate[basis];
cBasis = cBasis //. matrixProduct;

everything converges fine. But as soon as I compute

c = Table[If[i <= j, basis[[i]] cBasis[[j]], 0], {i, 1, 6}, {j, 1, 6}]

I get

$RecursionLimit::reclim: Recursion depth of 1024 exceeded.

How can I multiply basis[[i]] and basis[[j]] in a Table without triggering infinite rewrites? Any pointers to how to avoid the infinite recursion inside Table?

Thanks in advance for any insight!

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  • $\begingroup$ Hello, welcome to MMA.SE, then, please show us a self-contained (minimal) working example reproducing your problem, otherwise it'll be hard to diagnose. $\endgroup$ Commented Jun 15 at 14:18
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    $\begingroup$ Yeah, we're going to need to see more of your code, but in the meantime, I'm suspicious of how many times c appears in your code. I wouldn't be surprised if a c turned up inside the Table expression that you're using to define c. $\endgroup$ Commented Jun 15 at 15:05
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    $\begingroup$ And side note, C (uppercase) is a reserved symbol. It's probably not a problem in this specific case, but in general it's best to avoid name clashes with built-in symbols. If C had evaluation rules, then your replacement rules could be doing something very different. $\endgroup$ Commented Jun 15 at 15:08
  • $\begingroup$ The last rule inside matrixProduct looks dangerous. Because of the use of lots of BlankNullSequences (triple underscores like ___) it looks like that pattern might match the right-hand side of that same rule, leading to an infinite recursion. You might want to replace ___ with __ (double underscores, i.e. BlankSequence. $\endgroup$ Commented Jun 15 at 20:07

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