2016 Update

Task/Resistor-mesh/J/resistor-mesh-1.j

@@ -2,9 +2,11 @@ nodes=: 10 10 #: i. 100
 nodeA=: 1 1
 nodeB=: 6 7
 
+NB. verb to pair up coordinates along a specific offset
 conn =: [: (#~ e.~/@|:~&0 2) ([ ,: +)"1
-ref =: ~. nodeA,nodes-.nodeB
-wiring=: /:~ ref i. ,/ nodes conn"2 1 (,-)=i.2
-Yii=: _1 _1 }. (* =@i.@#) #/.~ {."1 wiring
-Yij=: - _1 _1 }. 1:`(<"1@[)`]}&(+/~ 0*i.1+#ref) wiring
-Y=: Yii+Yij
+
+ref =: ~. nodeA,nodes-.nodeB                    NB. all nodes, with A first and B omitted
+wiring=: /:~ ref i. ,/ nodes conn"2 1 (,-)=i.2  NB. connected pairs (indices into ref)
+Yii=: (* =@i.@#) #/.~ {."1 wiring               NB. diagonal of Y represents connections to B
+Yij=: -1:`(<"1@[)`]}&(+/~ 0*i.1+#ref) wiring    NB. off diagonal of Y represents wiring
+Y=: _1 _1 }. Yii+Yij

Task/Resistor-mesh/J/resistor-mesh-4.j

@@ -0,0 +1,28 @@
+   3 3 #: i.9
+0 0
+0 1
+0 2
+1 0
+1 1
+1 2
+2 0
+2 1
+2 2
+   (3 3 #: i.9) conn 0 1
+0 0
+0 1
+
+0 1
+0 2
+
+1 0
+1 1
+
+1 1
+1 2
+
+2 0
+2 1
+
+2 1
+2 2