connect last array element using [end]

[m.thorade@…]

I took the example Modelica.Electrical.Analog.Examples.HeatingResistor and removed the graphical part and renamed it, this gives me:

model End_connect
  Modelica.Electrical.Analog.Basic.HeatingResistor heatingResistor(R_ref=100, alpha=1e-3, T_ref=293.15, i(start=0));
  Modelica.Electrical.Analog.Basic.Ground G;
  Modelica.Electrical.Analog.Sources.SineVoltage SineVoltage1(V=220, freqHz=1);
  Modelica.Thermal.HeatTransfer.Components.ThermalConductor thermalConductor(G=50);
  Modelica.Thermal.HeatTransfer.Celsius.FixedTemperature fixedTemperature(T=20);

equation
  connect(SineVoltage1.n, G.p);
  connect(heatingResistor.heatPort, thermalConductor.port_a);
  connect(SineVoltage1.p, heatingResistor.p);
  connect(G.p, heatingResistor.n);
  connect(thermalConductor.port_b, fixedTemperature.port);

annotation (experiment(StopTime=5));

end End_connect;

This checks, translates and simulates just fine.
Now, I made every component an array and connect them as below:

model End_connect

  parameter Integer nEle=5;

  Modelica.Electrical.Analog.Basic.HeatingResistor heatingResistor[nEle](each R_ref=100, each alpha=1e-3, each T_ref=293.15, each i(start=0));
  Modelica.Electrical.Analog.Basic.Ground G[nEle];
  Modelica.Electrical.Analog.Sources.SineVoltage SineVoltage1[nEle](each V=220, each freqHz=1);
  Modelica.Thermal.HeatTransfer.Components.ThermalConductor thermalConductor[nEle](each G=50);
  Modelica.Thermal.HeatTransfer.Celsius.FixedTemperature fixedTemperature[nEle](each T=20);

equation 
  // connect first
  connect(SineVoltage1[1].n, G[1].p);
  connect(heatingResistor[1].heatPort, thermalConductor[1].port_a);
  connect(SineVoltage1[1].p, heatingResistor[1].p);
  connect(G[1].p, heatingResistor[1].n);
  connect(thermalConductor[1].port_b, fixedTemperature[1].port);

  // connect middle
  for i in 2:nEle-1 loop
    connect(SineVoltage1[i].n, G[i].p);
    connect(heatingResistor[i].heatPort, thermalConductor[i].port_a);
    connect(SineVoltage1[i].p, heatingResistor[i].p);
    connect(G[i].p, heatingResistor[i].n);
    connect(thermalConductor[i].port_b, fixedTemperature[i].port);
  end for;

  //connect last
  connect(SineVoltage1[end].n, G[end].p);
  connect(heatingResistor[end].heatPort, thermalConductor[end].port_a);
  connect(SineVoltage1[end].p, heatingResistor[end].p);
  connect(G[end].p, heatingResistor[end].n);
  connect(thermalConductor[end].port_b, fixedTemperature[end].port);

annotation (experiment(StopTime=5));

end End_connect;

This checks, translates and simulates just fine in Dymola, but not in OpenModelica.
Is this syntax wrong and should be fixed in my model? How?
Or is it a bug in OpenModelica?

Note: The same error appears e.g. here:
​https://libraries.openmodelica.org/branches/master/BuildingSystems/files/BuildingSystems_BuildingSystems.Technologies.ThermalStorages.Examples.FluidStorage.err

[Martin Sjölund]

Subscripts in a connector reference shall be parameter expressions or the special operator “:”

But end is not a parameter expression according to the specification (seems to be an error). Neither is size(X,N), but that works if you want something equivalent in your model (although more clunky to write).

Implementation note: The problem is that connectors use some special function instead of the general-purpose expression elaboration (I assume for performance reasons), and Expression.fromAbsynExp cannot represent end in any meaningful way since it needs type information to be evaluated (which this function lacks)... It could be represented by size(X,N) here (but only if the name of the variable and the dimension were passed along and the dimension has integer size).

I created ​m:#2206 to clarify what is allowed in the spec.

[Martin Sjölund]

@perost just showed me a 3.4 spec draft where they are parameter expressions. So yes, this seems to be an OM bug.

[anonymous]

Thanks for clarifying.

The link to th eModelica trac is broken, this is a working one:
​https://trac.modelica.org/Modelica/ticket/2206
​https://trac.modelica.org/Modelica/ticket/1082

Relevant sections in the 3.4 Spec:
section 3.8.2 and section 10.5.2
​https://modelica.org/news_items/release_of_modelica_3_4
​https://modelica.org/documents/ModelicaSpec34.pdf

[Matthis Thorade <m.thorade@…>]

We re-wrote the one single model in our library that used [end] in connect equations (which was easy, because the arrays were declared using a variable already).

Leaving this ticket open though, assuming you want to support usage of [end] in connect equations in the future.

[Matthis Thorade <m.thorade@…>]

Found another model with the same error message here:
​https://libraries.openmodelica.org/branches/master/BuildingSystems/files/BuildingSystems_BuildingSystems.Technologies.SolarThermal.Examples.BigCollectorInstallationWithStorage.err
That is now also rewritten.

[Per Östlund]

Using end in connect equations works just fine in the new frontend, so I guess this can be considered fixed.