[rob74]

> An often overlooked positive effect of macros is that the entire community can experiment with new language features.

Sure, that sounds positive - but with enough macros, you can turn "your" version of the language into something completely unrecognizable to people that are only familiar with the "basic" version (or, otherwise said: congratulations, you've got yourself a DSL!), and I would say that's a rather negative effect...

[shakna]

TeXInfo is a plain-TeX system that rewrites the parser to a completely new syntax, whilst maintaining compatibility with importing and linking to other libraries. It is extensively used, especially in emacs.

Having a DSL, isn't necessarily a bad thing.

[soegaard]

This is no different from having competing libraries for dates, regular expressions, html parsing etc.

[rob74]

That's the reason why many prefer "batteries-included" languages that provide a standard implementation for all the basic stuff...