From 66626df6e386476a56118e211e8c9bf4913d1ed5 Mon Sep 17 00:00:00 2001
From: "W. Trevor King" <wking@drexel.edu>
Date: Fri, 20 May 2011 13:57:05 -0400
Subject: [PATCH] Add TwoTerminal.shift() and kirchhoff_loop() to Circ.asy.

---
 asymptote/Circ-test.asy | 23 ++++++++++++++++++++---
 asymptote/Circ.asy      | 34 ++++++++++++++++++++++++++++++++--
 2 files changed, 52 insertions(+), 5 deletions(-)

diff --git a/asymptote/Circ-test.asy b/asymptote/Circ-test.asy
index 309dacc..e8030e0 100644
--- a/asymptote/Circ-test.asy
+++ b/asymptote/Circ-test.asy
@@ -23,9 +23,9 @@ real u = 2cm, v=0;
 
 write("resistor");
 TwoTerminal Rn = resistor((0,v), 0, normal, "$R_{normal}$", "30\ohm");
-dot("beg", Rn.beg, NW);
-dot("end", Rn.end, NE);
-dot("mid", Rn.mid, S);
+dot("beg", Rn.beg, NW, red);
+dot("end", Rn.end, NE, red);
+dot("mid", Rn.mid, S, red);
 TwoTerminal Rvb = resistor((2u,v), 0, variable, "$R_{variable}$", "30\kohm");
 v -= u;
 
@@ -98,3 +98,20 @@ dot("rlsq w/d", (4u,v), N);
 dot("b", (9u/2,v-u/2), S);
 wire((4u,v), (9u/2,v-u/2), rlsq, u/4);
 v -= u;
+
+write("circuit");
+v -= u/2;  // this circuit takes up more height than the previous lines.
+TwoTerminal Ccirc = capacitor((0,v), ang=90);
+TwoTerminal Rcirc = resistor(draw=false);
+Rcirc.centerto(Ccirc.beg, Ccirc.end);
+Rcirc.shift((u,0));  // gratuitous use of shift, but whatever...
+Rcirc.draw();
+// In the following, we assume the resistor is longer than the
+// capacitor.  If that is not true, you can find the corners of the
+// circuit programatically and use those corners.
+wire(Rcirc.end, Ccirc.end, rlsq);
+wire(Rcirc.beg, Ccirc.beg, rlsq);
+pair Pcirc[] = {(Ccirc.beg.x,Rcirc.beg.y), (Ccirc.end.x,Rcirc.end.y),
+		Rcirc.end, Rcirc.beg};
+kirchhoff_loop(Pcirc);
+v -= u;
diff --git a/asymptote/Circ.asy b/asymptote/Circ.asy
index 42c889e..6a9c2db 100644
--- a/asymptote/Circ.asy
+++ b/asymptote/Circ.asy
@@ -40,8 +40,9 @@ int labeling = rotatelabel;
 
 real linewd = 0.25mm;
 
-pen line = makepen(scale(0.5*linewd)*unitcircle);
-pen misc = makepen(scale(0.4*linewd)*unitcircle);
+pen line = linewidth(linewd);
+pen misc = linewidth(0.8*linewd);
+pen kirchhoff_pen = linewidth(10*linewd)+gray(0.7);
 
 // Arrowhead definitions
 
@@ -238,6 +239,13 @@ struct TwoTerminal {
     add(pic, picL, (end-beg)/2);
   }
 
+  /* Shift position by a */
+  void shift(pair a) {
+    this.beg += a;
+    this.end += a;
+    this.mid += a;
+  }
+
   /* Rather than placing the element with a point and direction (beg,
    * ang), center an element between the pairs a and b.  The optional
    * offset shifts the element in the direction rotated(90)*(b-a)
@@ -983,3 +991,25 @@ vardef rheostat@#(expr z,type,ang)=
 enddef;
 
 */
+
+// Loop symbols for Kirchhoff's rules.
+
+void kirchhoff_loop(picture pic=currentpicture, pair points[],
+		    pen outline=kirchhoff_pen, real aspace=-1) {
+  // draw kirchhoff loop underneath currentpicture
+  picture newpic;
+  int i;
+  guide g;
+  pair a = points[0] - points[points.length-1];  // arrow distance
+  if (aspace < 0)
+    aspace = 3*linewidth(outline);  // one dot diameter
+  real alength = max(0.5*length(a), length(a) - aspace - linewidth(outline)/2);
+  a = alength*unit(a);
+  pair astop = points[points.length-1] + a;
+  dot(newpic, points[0], scale(3)*outline);
+  for (int i=0; i < points.length; ++i)
+    g = g--points[i];
+  g = g -- astop;
+  draw(newpic, g, outline, Arrow(size=3*linewidth(outline)));
+  add(pic, newpic, above=false);
+}
-- 
2.26.2