Don't want to have to go back to the top of a page to load a module to use a macro? Define the macro in etc/page.m5, so it's available to every page! But hold on — any changes to the macro will cause the entire site to be rebuilt, because almost everything uses etc/page.m5.
You can avoid that by keeping the macro in a separate module, but defining a loader with the same name in etc/page.m5:
# In etc/page.m5 define(`IMPLNOTE', `load(`implnote')\ indir(`$$0'$$!?@$$?@)')
# In etc/implnote.m5 define(`IMPLNOTE', ``This is an implementation note.'')
Your page will now only depend on
etc/implnote.m5 if it uses IMPLNOTE.
The idiom is likely to be well used, so a predefined
macro autoload is available to
do the work for you, with the first argument being the
module to load, and remaining arguments being macros
defined by it:
# In etc/page.m5 autoload(`implnote', `IMPLNOTE')\
But there's still a problem. Adding a new loader to etc/page.m5 also will cause the entire site to be rebuilt. The solution is to ensure your site is up-to-date first, then define the loader, then touch all your targets so they won't be rebuilt. Then touch the sources of pages that use the new macro. If it's truly new, that won't be very many!
More robustly, you could place your auto-loading macros in a separate module:
# In etc/pagesys.m5 autoload(`implnote', `IMPLNOTE')\
…and then load it from their original location without recording dependencies:
# In etc/page.m5 loadsys(`pagesys')\
The first argument of autoload is the name of the user module to
load, and all remaining arguments are names of macros
defined by that module. Note that autoload does nothing if the module has
already been loaded, so it won't destroy real
definitions if it happens to be expanded after the
module has been loaded.
