gEDA-dev: Clarity or Sanity?

[al davis]

On Wednesday 06 June 2007 17:20, Peter Clifton wrote:
> Adding a special attribute to be used in symbols which
> means "go read  this scheme code". (Or alternatively, "here is
> some scheme code"). 

What is the benefit?

> I believe this will be handy for allowing custom attribute
> helpers  for different classes of symbol, without having to
> add everything in  scheme files shipped with gschem.
> For example, a resistor symbol might include "resistor.scm"
> (which is then found somewhere in a particular search path),
> and this scheme code could provide the helper functions for
> filling in the attributes.

How about adding a list of legal attributes with range?  Make 
this a general feature that is available to all symbols.

Actually, even this leads to problems.  You might want to use a 
different technology than the symbol maker intended.  As an 
example, with discretes, capacitors typically are in picofarads 
or bigger.  On an IC, capacitors are typically in femtofarads.

> Alternatively - you might see this as useful, adding in a
> gnucap directive symbol might set a variable which allows the
> various helper  functions to show more simulation specific
> options. 
>
> We'd obviously need to make that setting go away again if you
> removed  the gnucap directive.

The schematic should not have anything that is simulator 
specific.  In particular, I really object to embedding 
simulator commands in the schematic.  Even the single 
attribute "value" where you put the simulator's text for the 
value, is too simulator specific.

If you must put something that indicates things like "transient 
analysis", have symbols like oscilloscope, DC voltmeter, 
ammeter, etc.  Then let the netlister decide how to convert to 
simulator commands.  These symbols are primarily for beginning 
users, who might be making the transition from something like 
Multi-sim.

I always either run the simulator interactively, or do multiple 
runs in a script.  Having a box in the schematic where you put 
simulator commands really only gets in the way.  Also, often I 
change the circuit through the simulator based on the results.

One feature I would really like is a way to back-annotate those 
changes, a way to update the schematic other than manually 
changing the values.