Hi,

For a calculation I'm trying to do, I have an 11d space whose (flat/tangent space) indices are split as follows

$M = (a, \mu, 11)$

$M = 0, 1, \ldots, 11$ (the full 11d flat index)

$a = 0, 1, 2, 3, 4, 5$ (a 6d subspace)

$\mu = 6, 7, 8, 9$ (a 4d subspace)

(11 is separated out)

What I'd like to do is have `split_index`

split an expression of the form $T_M S^M$ (or $T_M S_M$) into

$T_{a}S^{a} + T_{\mu}S^{\mu} + T_{11}S^{11}$

So far, what I have is

```
{M,N,P,Q,R,11}::Indices(full,flat,elevenD).
{a,b}::Indices(sixD,parent=elevenD).
{\mu,\nu,\rho}::Indices(fourD,parent=elevenD).
ex:=T_{M} S^{M};
split_index(_, $M,a,\mu$);
```

the output is

$T_a S^a + T_\mu S^\mu$

whereas of course what I'd like is

$T_a S^a + T_\mu S^\mu + T_{11} S^{11}$

I know that `split_index`

can be used to split into only two subsets.

So, I tried the following

```
{M,N,P,Q,R,11}::Indices(full,flat,elevenD).
{a,b}::Indices(sixD,parent=elevenD).
{\mu,\nu,\rho,11}::Indices(fiveD,parent=elevenD).
{\mu,\nu,\rho}::Indices(fourD,parent=fiveD).
```

but this too produces the same output as before.

**How can a three (or more) subset split be achieved?**

Any ideas, suggestions are welcome, including criticism of (any redundancy in?) the above code! Thanks!