Creating a namespace and copying another

[petermsiegel]

Is there documentation on what exactly causes NONCE ERRORS when copying namespaces using the standard formula:

'namespace' ⎕NS another_namespace

It seems as if some namespaces can't be copied (on the RHS), and I'm guessing it has to do with recursive namespaces (i.e. namespaces within "another_namespace"), but I'm not sure. To get around, I simply create a slightly convoluted expression to copy in another_namespace's items of nameclasses (⎕NC) 2 3 4, but not (sadly) 9.

My question is really two-- (1) what is going on and (2) where is it documented (with apologies for missing an obvious location despite brute-force searches for NONCE ERRORS). CHEERS!