-I need to look at the full range of things that other wikis use their plugin systems for, but preprocessor directives as plugins certianly seems useful, even if it's not a complete solution.
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-## case study: Moin Moin plugins
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-See <http://moinmoin.wikiwikiweb.de/MoinDev/PluginConcept>
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-6 different types of plugins:
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-* *actions* are possibly out of scope for ikiwiki, this is probably what it uses for cgi script type stuff. Unless ikiwiki wants to allow pluggable CGI script stuff, it doesn't need these.
-* *parsers* and *formatters* are basically what I've been calling [[PluggableRenderers]]. MoinMoin separates these, so that a page is parsed to (presumbly) some intermediate form before being output as html or some other form. That's a nice separation, but what to do about things like markdown that are both a parser and a formatter?
-* *macros* and *processors* are analagous to preprocessor directives. A processor can operate on a large block of text though.
-* *themes* should be irrellevant (ikiwiki has [[templates]]).
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-## case study: pybloxsom plugins