====== Minimal Word Set ======

How many primitives does a Forth need to get it started?

Surprisingly few, as you can see with Gforth EC, which provides a high-level
definition for almost every primitive.
But beware! If you omit too much, you risk circular behaviour (loops).

We need in any case:

'':dodoes'' as generalized entry point for all high-level definitions, or

''Call'' for primitive-centric implementations. 

''@'' and 
''!'' to access the memory. 

''>R'' and ''R>'' for the return stack, so anything can be moved. 

''+'' or 
''2*'' for Artihmetik. 

And ''NAND'' as a universal bit instruction. 

''?BRANCH'' or 
''0='' for branches. 

And finally '';S'' and 

''EXECUTE'' for execution.

Everything else can be defined from these words, even if it then needs temporary variables:

  : lit' r> @ ;
  : cell lit' [ 2 , ] ; \ oder 4 oder 8 ...
  : tmp1 lit' [ here cell+ , 0 , ] ;
  : dup tmp1 ! tmp1 @ tmp1 @ ;
  : lit r> dup cell + >r @ ;

By Bernd Paysan, Translation Juergen Pintaske 2015_11_21