documentation update about tcleval(...) tcl substitution of attributes by get_tok_value()

doc/xschem_man/component_property_syntax.html

@@ -184,6 +184,19 @@ name="mchanged_name" model=\"nmos\" w="20u" l="3u" m="10"
       This is mainly used for tedax, where by back annotation a connection to a symbol must be changed.
       This notation is faster since xschem does not have to find a pin by string matching.</p>
  </ul><br>
+
+ <h3>TCL ATTRIBUTE SUBSTITUTION</h3>
+
+  <p>
+   Any attribute and symbol text can be embedded in a <kbd>tcleval(....)</kbd> construct, the string inside the
+   parentheses will be passed to the tcl interpreter for evaluation. This allows to use any tcl 
+   variable/command/expression. Example: <br>
+  <kbd>value="tcleval([expr {[info exists ::resval] ? $::resval : {100k}}])"</kbd><br>
+  this attribute will set <kbd>value</kbd> (example: value of a resistor) to 100k if global tcl variable
+  <kbd>resval</kbd> is not set or to the value of <kbd>resval</kbd> if set.
+  </p>
+
+
  <!-- end of slide -->
  <div class="filler"></div>
 </div>

doc/xschem_man/symbol_property_syntax.html

@@ -458,6 +458,16 @@ verilog_format="xnor #(@risedel , @falldel ) @name ( @@Z , @@A , @@B );"
    this expandes to the <b>Verilog</b> global property string of the schematic containing the symbol
   </p>
  </ul><br>
+ <h3>TCL ATTRIBUTE SUBSTITUTION</h3>
+
+  <p>
+   Any attribute and symbol text can be embedded in a <kbd>tcleval(....)</kbd> construct, the string inside the 
+   parentheses will be passed to the tcl interpreter for evaluation. This allows to use any tcl 
+   variable/command/expression. Example: <br>
+   <kbd>spice_ignore="tcleval($::ignore_symbol)"</kbd> <br>
+   will cause the symbol to be ignored by the spice netlister if the <kbd>ignore_symbol</kbd> tcl variable is 
+   existing and set to <kbd>true</kbd>
+  </p>
 
  <!-- end of slide -->
  <div class="filler"></div>