Hey, all —
A while ago I noticed Jeremy expressing some regrets about how TiddlyWiki
has become dependent on text substitution macros, and suggesting that TWX
will do something differently:
*Jeremy Ruston:*
Thus, there are lots of quite prominent features that were introduced early
> on and that I would now handle differently (eg, the fact there is a
> difference between transclusion and the view widget, or the presence of
> text substitution macros which I now think was a mistake).
>
Having developed a lot of things in TW *and* reviewed the widget
architecture with an eye for performance, I have to agree. People across
the experience gamut seem to routinely stumble on the order-of-operations
involved in parsing widgets and expanding macros. I'm also speaking as a
compiler-designer: I've made the mistake of letting macros stand in for
functions in a language I've designed, and it was a problem for both
maintainability and performance.
I view TiddlyWiki as a functional programming system, where each widget is
a node with some parameters (attributes, parse tree / children) and a
result (DOM tree). Macros are the de-facto stand in for programmable
subroutines, but they are unstructured and must be re-parsed whenever they
appear. Transcluded tiddlers may also behave like subroutines, and while
they're structured they don't support explicit parameters.
The solution I anticipate would be to introduce a "wiki-function" entity
which is pre-parsed and whose invocation does nothing more than set a few
variables and instantiate its parse tree into widgets. Perhaps something
like this, widget-wise, with a WikiText syntax to get rid of the
boilerplate:
<$function $name="tablerows" filter>
<$list filter=<<filter>> >
<tr>
<th>{{!!title}}</th>
<td>{{!!field1}}</td>
<td>{{!!field2}}</td>
</tr>
</$list>
</$function>
<table>
<tr>
<th>Title</th>
<th>field1</th>
<th>field2</th>
</tr>
<tr><th colspan=3>Important Stuff</th></tr>
<$call $name="tablerows" filter="[tag[Tag1]tag[Important]]" />
<tr><th colspan=3>Less-Important Stuff</th></tr>
<$call $name="tablerows" filter="[tag[Tag1]!tag[Important]]" />
</table>
Now, this *does* look basically the same as a macro call. The differences
are crucial, though: lower parsing and refresh overhead, only <<one
syntax>> for variables, and no gotchas with quoting, whitespace,
order-of-operations or open markup. As far as I'm concerned, the
similarity in usage could make transitioning trivial in many cases and the
more consistent behavior could make TiddlyWiki "programming" much easier to
learn.
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