Re: gEDA-user: Matching footprints with symbols

[Armin Faltl <armin.faltl@xxxxxx>]

Hi,

keeping to my promisse, I came up with a skeleton in "pseudo-html"
(lacks some markup for readability as text) on identifiers and names.

It contains the information I learned in the last week(s) and, if fully
filled with authoritative information could form the chapter on identifiers
in gEDA-interfaces in a gEDA handbook.

Best Regards, Armin

P.S.: I'm a big fan of good offline documentation. A downloadable set
       of HTML-pages like e.g. PostgreSQL has it is one of my favourites.


Armin Faltl wrote:
> OMG, it works!
>
> Thanks Stefan for all the help. Now the weekend has started.
>
> I'll start a "Naming conventions and restrictions" page to
> describe this and put on the wiki. In the long run, this should
> be fixed in the parser(s) though.
>
> Best Regards, Armin
<h2>Conventions and Limitations on Identifiers in gEDA</h2>

<p>
To give a definition, an identifier is a string entity,
that servers as attribute or value or name assigned
to an object alone or in combination with other identifiers
to describe it in a given context.

Examples are symbol attributes and their respective values
and file-names.
</p>
<h3>Composition of an Identifier</h3>
<p>
As any string an identifiers is composed of characters
with the distinction, that while a string may contain
any representable character in an alphabet, an identifier
must use a reduced set of characters and in some cases additional
restrictions exist, on the relative position of certain
characters in the identifier.
This serves the purpose, to reserve characters outside
the set allowed for identifiers for other syntactic
purposes than naming.
</p>
<p>
The different interfaces in gEDA without exception use
identifiers - however, as of now the allowed charset
and some other restrictions are not the same for
every interface, so the interfaces themselves are listed
here with detailed description of each of them later on:
<ul>
  <li>file names of several categories</li>
  <li>symbol names in schematics in gschem</li>
  <li>symbol- and other attributes in schematics</li>
  <li>values of attributes in schematics</li>
</ul>
</p>
<p>
To actually note the character sets, the syntax of Perl regular expressions
is used.
</p>


<h4>file names of several categories</h4>

<h5>Schematics</h5>
<p>
All valid filename-prefixes of the underlying operating system are allowed.
The Suffix is generally '.sch'
</p>

<h5>Footprint files of "newlib"</h5>
<p>
The suffix for footprint files is generally '.fp'.<br>
<!-- fill in lengthy explanation here, how/why fp's with no suffix at all... -->
While it is possible to use any prefix allowed by the OS, it is unwise
to use '-' (dash) and ' ' (blank) since problems with these have been
experienced occasionally.
</p>

<h4>symbol names in schematics in gschem</h4>
<p>
<!-- here an indication of what versions of gschem this pertains to is due -->
The allowed characters in a symbol name are:

	[-_.+a-zA-Z0-9] <-- this is a guess and by no means authoritative

Assumed restrictions by me, Armin:
<ul>
<li>must not end in a '-', since this is used for backups</li>
<li>maximal length <= N ???</li>
<li>on MS-Windows case sensitive names may be a problem</li>
</ul>
<!-- (- ah yes, these backup files, how they are named is a mess as well -
never saw #whatever.some# before ;-) -->

This <a href>convention on naming</a> shall help the understanding and
exchange of symbols.
</p>


<h4>Symbol- and other Attributes in Schematics</h4>

<h4>Values of Attributes in Schematics</h4>
<p>
<b>CAVEAT:</b></br>
If the schematic has to be converted to a board file (.pcb) for
use with 'pcb', the value of the "ref_des" attribute in gschem-symbols
must end in a digit ([0-9] - [1-9]?)!
</p>


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