[ZPT] [Weakness] "metal:fill-slot" and "metal:use-macro" not together

[Evan Simpson]

Dieter Maurer wrote:

> Currently, ZPT refuse to have
> "metal:fill-slot" and "metal:use-macro" together on one element.
> 
> This is unfortunate, because it is quite natural to
> fill a slot with a macro call


I agree.  I'm trying to straighten out several METAL implementation 
details over the next week, and this is one of them.

It is my intention that METAL will work like this:

During parsing:

1. 'define-macro' and 'use-macro' are always valid, subject to #3.

2. 'fill-slot' is only valid in a 'use-macro', and 'define-slot' is only 
valid in a 'define-macro'.

3. Inside a 'use-macro', all METAL statements other than 'fill-slot' are 
ignored.

As a consequence, macro definitions can be nested within each other, 
within slot definitions, and within filled slots.  Macro *uses* can only 
be nested by using one in the filled slot of another, since the rest of 
a macro use body is placeholder text.

During source macro expansion:

1. METAL statements in the page are left unchanged.  METAL statements in 
expanded macros are stripped out.

This means that if you use a macro that has embedded macro definitions, 
or that uses other macros itself, none of that METAL markup will appear 
in the expanded macro text.

Cheers,


Evan