Index: trunk/doc/examples/non-graphical/index.html
===================================================================
--- trunk/doc/examples/non-graphical/index.html	(revision 7098)
+++ trunk/doc/examples/non-graphical/index.html	(revision 7099)
@@ -3,7 +3,8 @@
 
 <h1> Non-graphical sheets - proposals </h1>
 <p>
-<b> This is a proposal at this stage - any detail may change any time </b>
+<b> This is a proposal at this stage - any detail may change any time. This
+feature is not yet implemented. </b>
 <p>
 Sometimes a design is easier specified by text than drawing. Typical examples:
 <ul>
@@ -61,6 +62,55 @@
 of combining graphical and non-graphical sheets: U5 is a network of gates
 that controls chip-select; it's better drawn for clarity.
 
+<h2> fawk (turing complete) </h2>
+<p>
+In some cases parts of the design can be specified using repetitive patterns.
+An easy way to handle this is to write a script that generates a graphical
+sheet or a non-graphical sheet using a declarative sytnax.
+<p>
+If that script is written in fawk, sch-rnd can run it without having to
+generate and parse the declarative intermediate. This feature is limited
+to fawk because:
+<ul>
+	<li> fawk is always available in librnd
+	<li> fawk supports execution limit and memory allocation limit so opening
+	     a non-graphical sheet specified as a fawk script is safe, an attacker
+	     won't be able to force sch-rnd into an inifinite loop or into allocating
+	     all system memory.
+</ul>
+<p>
+A simple example script, <a href="r2r.fawk">r2r.fawk</a> generates
+5 bits of the classic R2R DAC. It can be configured by changing the values
+in main().
+<p>
+The script doesn't emit a netlist or declarative tEDAx non-graphical sheet.
+The result can be observed in sch-rnd by loading only the fakw script
+as a sheet and using the abstract model dialog.
+<p>
+(An alternative is implementing the cschem functions locally, as vararg
+fawk funcitons and make them print to stdout using fawk_print(). Then the
+script can be ran and debugged independently of cschem, using the example
+libfawk command line interpreter.)
+<p>
+Functions provided by sch-rnd:
+<table border=1 cellspacing=0>
+	<tr> <th> function <th> description
+	<tr> <td>acomp_attr(name,   key, val, ...);
+	     <td>create a component by name, or add to existing component by that name;
+	         add key=val pairs of attributes; this is a vararg function.
 
+	<tr> <td>anet_attr(name,   key, val, ...);
+	     <td>create a network by name, or add to existing network by that name;
+	         add key=val pairs of attributes; this is a vararg function.
+
+	<tr> <td>aconn(netname,   compname, termname, ...);
+	     <td>create a network by netname, or extend existing network by that name;
+	         connect terminal(s) addressed by (compname-termname); this is a vararg function.
+
+</table>
+
+
+
+
 </body>
-</html>
\ No newline at end of file
+</html>
Index: trunk/doc/examples/non-graphical/r2r.fawk
===================================================================
--- trunk/doc/examples/non-graphical/r2r.fawk	(nonexistent)
+++ trunk/doc/examples/non-graphical/r2r.fawk	(revision 7099)
@@ -0,0 +1,56 @@
+## cschem fawk sheet
+
+# The first line must be the above, else cschem will refuse to run the script.
+
+# Generate classic R2R digital-analog-converter
+#
+# input0        input1        input2
+#   |             |             |
+#  [R1]          [R3]          [R5]
+#   |             |             | 
+#   j0 -- [R2] -- j1 -- [R4] -- j2 -- ...
+#   |
+#  [R0]
+#   |
+#   gnd
+#
+# R0, R1, R3, R5, ... are 2*R resistors (2k0 by default)
+# R2, R4, ... are 1*R resistors (1k0 by default)
+# output is the last j
+
+function refdes(n)
+{
+	return "R" @ (base + n);
+}
+
+function resistor(n, val,       rfd)
+{
+	rfd = refdes(0);
+	acomp_attr(rfd,   "value", val,   "footprint", fp);
+}
+
+function main(ARGV)
+{
+	bits=5;
+	valr =  "1k0";
+	valr2 = "2k0";
+	base = 100;
+	fp = "0805";
+
+	# create leftmost divider
+	low = resistor(0, valr2);
+	high = resistor(1, valr2);
+	aconn("gnd", low, 1);
+	aconn("input0", high, 2);
+	aconn("j0", low, 2, high, 1);
+
+	# create the rest of the ladder, piece by piece from the horizontal
+	# R resistor and ther vertical 2*R resistor
+	for(i = 1; i < bits; i++) {
+		horiz = resistor(i*2+0, valr);
+		vert  = resistor(i*2+1, valr2);
+		aconn("j" @ (i-1), horiz, 1);
+		aconn("j" @ i, horiz, 2, vert, 1);
+		aconn("input" @ i, vert, 2);
+	}
+}