[Webmacro-devel] Run-time #macros

[Brian G. <br...@qu...>]

Marc has raised an issue that no one else has so far regarding #macro.
He wants to write #macros to traverse DOM style trees at runtime.  You
can do this more clumsily with (lazy) #include, but that's kind of
nasty.

Justin had floated an idea at one point for a directive like #template:
where you could say

  #template {
    blah blah $a blah $b
  }

in a template, and then #include it later in the template.  It was a
crude macro facility with no substitution, or an #include facility
without using ancillary files.

Another suggestion made at one point would be to allow some sort of
substitution with #include -- like this (assuming a map-style syntax):

#include "foo.wm" using [ $a => "foo", $b => "moo" ] 

which would be like

#push $a
#push $b
#set $a = "foo"
#set $b = "moo"
#include "foo.wm"
#pop $b
#pop $a

Where #push and #pop do the obvious thing.  

Or, perhaps this is a better syntax for a temporary substitution:

#with ($a="foo", $b="bar") {
  #include "foo.wm"
}

Combining these would get the tool that Marc is looking for (lets
calls these Marcros.)  However, I think its worth having a discussion
about whether this is a good thing.  We don't even have a loop
directive because we don't want to put users in a situation where they
can create infinite loops at run time.