DIP 50 - AST macros

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On Thursday, 14 November 2013 at 09:12:38 UTC, Walter Bright 
wrote:
> I do understand this. I've not only extensively used macro 
> systems, I've designed two successful ones and implemented 
> other peoples' designs.
>
> I've also seen the sheer awfulness of what happens with these 
> systems over the long term. The fascinating thing about this 
> awfulness is people are well aware of it in everyone's macro 
> libraries but their own.

What kind of macro systems are you talking about? C-like macros? 
Assembly macros? Lisp-like macros? It seems that Jacob's proposed 
system is similar to none of these.