Nested components in macros (WAS: Re: [Freemarker-devel] interested in feedback with new template engine)

>>>> Also, I am not terribly good at writing friendly documentation and
>>>> would appreciate anyone that would like to participate in the  
>>>> growth
>>>> of this project with me especially in the docs area...
>>>>
>>>> Some of the features that I have address are:
>>>>
>>>> - can define macro parameters as nested components (which gives you
>>>> the ability to create complex UI components)
>>>
>>> I'm not sure I understand what does this mean. For FM 2.4, we do  
>>> have
>>> curried macros though, if that's what you had in mind.
>>
>> Well it was discussed a lot earlier, although certainly only me and
>> Joe was responsive in that thread. I count this thing among those  
>> that
>> the two main FM guys (or of three) don't get for unexplained reasons,
>> like #nested earlier.
>
> I guess I never felt that there was a clear proposal that I could just
> sit down and implement. (Though maybe there was and I wasn't paying
> attention.)

That is what I suggested--

I propose to add the following to macro:

<#tagged> (call it fragment if you like)

That tells FreeMarker to insert a tagged content. You would use it  
like that:


* <#macro main> *
*  <table> *
*    <tr> *
*      <td colspan="2"><#tagged></td> *
*    </tr> *
*    <tr> *
*      <td><#tagged></td> *
*      <td><#tagged></td> *
*    </tr> *
*   </table> *
* </#macro> *

* <@main ; content1, content2, content3> *
*  <@content1>This content 1</@content1> *
*  <@content2>This content 2</@content2> *
*  <@content3>This content 3</@content3> *
* </@main> *

FreeMarker needs to ensure that all <#tagged> occurrences have a  
matching block in the invocation of the macro and the blocks come in  
the correct order.


>
>> Anyway, here you will find an example:
>>
>> http://code.google.com/p/zipscript/wiki/FreemarkerComparison
>>
>
> The syntax implemented seems rather odd. What distinguishes the inner
> parameter or component from simply another macro invocation?
>
> At some point earlier, I had an implementation of something similar,
> but with a new directive called #fragment and then you put a fragment
> in your macro invocation and you optionally could invoke #nested with
> a fragment="fragmentname" specifier and it would do the nested body of
> the fragment instead.
>
> I later pulled it out because I was redoing so many things that I
> figured I'd put this back in later (or not) after the cleanup.
>
> I am seeing some amount of need for this because I am working on a new
> project called KawaDD, a fork of JavaCC (I had to fork because the
> people there were impossible) and I want to encapsulate eventually
> some language constructs and then you start realizing that something
> like try-catch-finally is actually a try block plus one or more catch
> blocks plus a finally block, so multiple inner blocks to the macro
> seems necessary to capture it cleanly.
>
> Now that you've had even more time to think about it, how would you
> like to see it work?

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