8G. initialisation
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1. Always initialised to NIL (or else, if explicitly stated)
   - global variables
     NOTE: for documentation purposes, it's always nicer if you
     write =NIL in the definitions of variables that you expect to be NIL.
2. Initialised to '' and [] resp.
   - global and local STRINGs
   - global and local LISTs
3. Not initialised
   - local variables (unless explicitly stated)
   - global and local ARRAYs
   - global and local OBJECTs