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Parameter strings in initial algorithm

#6087  Permalink Top

Parameter strings in initial algorithm

Jul-30-15 08:23:25

Hey everyone, new modelica user here.

I've been trying to initialise a String parameter within an initial algorithm section, for example:

Code:


model Fail

    parameter String x(fixed=false);

initial algorithm

    x := "please work";

end Fail;

But it won't simulate.  I get errors:

Code:


"Simulation execution failed for model: Fail

LOG_INIT          | error   | The initialization problem is inconsistent due to the following equation: 0 != 1 = not x == $TMP_x_1

stdout            | warning | Error in initialization. Storing results and exiting.

|                 | |       | Use -lv=LOG_INIT -w for more information.

"

and

Code:


Warning: Parameter x has no value, and is fixed during initialization (fixed=true), using available start value (start="") as default value.

Warning: The initial conditions are over specified. Use +d=initialization for more information.

It is as if 'fixed' gets forced to true for some reason.  However if I instead try the same thing with a Real it works:

Code:


model Pass

    parameter Real x(fixed=false);

initial algorithm

    x := 10;

end Pass;

Does anyone know why this is the case?  I would like to do this because I would like to conditionally set the string parameter.  If anyone has an alternative approach that would be welcome also.

Thanks

#6088  Permalink Top

Re: Parameter strings in initial algorithm

Jul-30-15 08:36:56

That is because there is no fixed attribute for string type. See section 4.8.4 in Modelica specification:

Code:


4.8.4 String Type

The following is the predefined String type: 

type String // Note: Defined with Modelica syntax although predefined

   StringType value;                    // Accessed without dot-notation

   parameter StringType  quantity    = "";

   parameter StringType start = "";     // Initial value

end String;

#6089  Permalink Top

Re: Parameter strings in initial algorithm

Jul-30-15 08:38:43

I think your model shouldn’t have passed the front end. So we should probably add a ticket about it anyway.

#6090  Permalink Top

Re: Parameter strings in initial algorithm

Jul-30-15 08:49:25

OK thanks.  I did a bit more reading on fixed and it seems to make a bit more sense now.  I found another way of doing what I originally wanted:

Code:


parameter String x = if 3 > 1 then "it" else "works";

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