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This is an excellent explanation.

As you say, if we assume that my set of macros are the machinery, then truly my "BRAINFUCK()" macro is Turing complete.

Using this distinction between language and machine, how peculiar that a Turing Complete thing can be expressed using a language which is not Turing Complete itself.

The question is really - are these distinctions between machine and language always meaningful and without contradiction.

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Using this distinction between language and machine, how peculiar that a Turing Complete thing can be expressed using a language which is not Turing Complete itself.

Ah, but that's the rub: we can't, and we didn't. You are imparting semantics on your macros that the C preprocessor has not. That is, the semantics that you imagine the macros to have are solely in your mind. They are not implied by the semantics of the C preprocessor.

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