Experimental Physics and
Industrial Control System

Benjamin Franksen <[email protected]> · Sat, 17 Dec 2005 01:50:40 +0100

Dear Andrew,

I agree with most of what you say, however

you wrote:
> This may be related: In about R3.14.6 we extended macLib so the macro
> expansion syntax may also include a default value, in the form
> $(name=value). The default is used if no macro by that name is found.
>  I suspect this syntax has not been introduced to VDCT yet, and I can
> see that it would cause some complications if you're expecting an
> undefined macro that has a default to remain as a macro in the
> instanciation - maybe you never should.

and later

> I don't like your idea of trying to separate out what you're calling
> a "port macro" and a "string substitution macro" - I assume the
> latter is intended for expansion only in a dbLoadRecords() statement.
>  I don't think you can make this kind of distinction though; in some
> cases the template may have all its macros expanded on the host by a
> parent.vdb file, and in others the same template parameters may be
> provided to dbLoadRecords().

which is somewhat contradictory, I'd say. In the second paragraph you 
give a very good reason why retaining an undefined macro makes a lot of 
sense (i.e. because I might want to give a value only later e.g. in the 
startup file). Or do you propose that in every such case eitehr the 
template has a definition a la $(name=$(name)) or the substitution must 
be name=$(name)? That would be boring, wouldn't it?

Ben

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System