Add possibility to have current through resistor - PR #56

Author: svenboulanger

SpiceSharpBehavioral/Components/BehavioralBindingContext.cs

@@ -88,30 +88,46 @@ public IVariable<T> MapNode<T>(IVariableFactory<IVariable<T>> factory, VariableN
 
                 case NodeTypes.Current:
                     IBehaviorContainer container;
+                    IBiasingBehavior tmpb;
+                    IFrequencyBehavior tmpf;
+                    
+                    // Get the relevant behaviors
                     if (Simulation.EntityBehaviors.Comparer.Equals(node.Name, Behaviors.Name))
                         container = Behaviors;
                     else
                         container = Simulation.EntityBehaviors[node.Name];
+
                     if (container == Behaviors)
                     {
                         if (ownBranch == null)
                             throw new SpiceSharpException($"The behavior for {Entity.Name} does not define a branch current.");
                         return ownBranch;
                     }
                     else if (container.TryGetValue<IBranchedBehavior<T>>(out var branched))
+                    {
+                        // Best-case scenario! Our behaviors define a branched behavior!
                         return branched.Branch;
-                    else if (typeof(T) == typeof(double) && container.TryGetValue(out IBiasingBehavior tmpb) && tmpb is CurrentSources.Biasing biasing)
+                    }
+                    else if (typeof(T) == typeof(double) && container.TryGetValue(out tmpb) && tmpb is CurrentSources.Biasing biasing)
                     {
+                        // If whatever is being is asked is the current from a current source, then we also don't have a problem
                         var result = new FuncVariable<double>($"I({biasing.Name})", () => biasing.Current, Units.Ampere);
                         return result as IVariable<T>;
                     }
-                    else if (typeof(T) == typeof(Complex) && container.TryGetValue(out IFrequencyBehavior tmpf) && tmpf is CurrentSources.Frequency frequency)
+                    else if (typeof(T) == typeof(Complex) && container.TryGetValue(out tmpf) && tmpf is CurrentSources.Frequency frequency)
                     {
+                        // Current source = no problem
                         var result = new FuncVariable<Complex>($"I({frequency.Name})", () => frequency.ComplexCurrent, Units.Ampere);
                         return result as IVariable<T>;
                     }
                     else
-                        goto default;
+                    {
+                        var result = container.CreatePropertyGetter<T>("i");
+                        if (result == null)
+                            goto default;
+                        SpiceSharpWarning.Warning(this, SpiceSharpBehavioral.Properties.Resources.LooseLinkCurrent.FormatString(container.Name));
+                        return new FuncVariable<T>($"@{container.Name}[i]", result, Units.Ampere);
+                    }
 
                 default:
                     throw new SpiceSharpException($"Could not determine the variable {node.Name}");

SpiceSharpBehavioral/Properties/Resources.Designer.cs

@@ -120,4 +120,7 @@
   <data name="ArgumentMismatch" xml:space="preserve">
     <value>Invalid number of arguments: {0} expected but {1} were given.</value>
   </data>
+  <data name="LooseLinkCurrent" xml:space="preserve">
+    <value>The current through {0} is only loosely linked. This might result in less accurate results, or instability. Consider placing a voltage source in series and referencing the current through that instead.</value>
+  </data>
 </root>

SpiceSharpBehavioral/Properties/Resources.resx

@@ -1,13 +1,8 @@
 using NUnit.Framework;
 using SpiceSharp;
 using SpiceSharp.Components;
-using SpiceSharp.Entities;
 using SpiceSharp.Simulations;
 using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
 
 namespace SpiceSharpBehavioralTest.Components
 {
@@ -111,5 +106,31 @@ private static void Entry(Circuit ckt, string name, string m_in, string m_out, s
             ckt.Add(new BehavioralCurrentSource($"{name}.Guv", "0", v_vel, vel($"V({mss})")));
             ckt.Add(new Resistor($"{name}.Ruv", "0", v_vel, 1.0));
         }
+
+        [Test]
+        public void When_ResistorCurrent_Expect_ReferenceWarning()
+        {
+            var ckt = new Circuit(
+                new VoltageSource("V1", "in", "0", 1.0),
+                new Resistor("R1", "in", "0", 1e3),
+                new BehavioralVoltageSource("V2", "out", "0", "I(R1)"));
+
+            // Catch the warning
+            int warnings = 0;
+            SpiceSharpWarning.WarningGenerated += (sender, args) =>
+            {
+                warnings++;
+            };
+
+            // Run the simulation
+            var op = new OP("op");
+            op.ExportSimulationData += (sender, args) =>
+            {
+                Assert.AreEqual(1.0 / 1e3, args.GetVoltage("out"), 1e-9);
+            };
+            op.Run(ckt);
+
+            Assert.AreEqual(1, warnings);
+        }
     }
 }