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Hi,

 

I have a String Parameter with index domain “i” called “ModPrefix” containing prefixes of modules within my project. Each of this modules has a variable with the name “Q”. Now, I would like to access these variables within the definition of a Node called “FacilityNode” like

NetOutflow = ModPrefix(i)::Q

However, this leads to the error

The identifier "Q" has not been declared, but it is declared in the modules d...].

where I replaced the names of the modules with “h...]”.

 

My idea of a workaround was an if-then-else-statement like

NetOutflow = 
    if ( ModPrefix(i) = "prefix1" ) then
        prefix1:Q
    elseif ( ModPrefix(i) = "prefix2" ) then
        prefix2:Q
    else
        0
    endif;

in the case of two modules with prefixes “prefix1” and “prefix2”. However, I would still like to know if there is a way to circumvent it-then-else-statements, since they become ugly in the case of many modules.

 

 

Hi,

Hope this helps:

NetOutFlow =
    ScalarValue(
        StringToElement( 
            AllIdentifiers,
            formatString("%s::Q", ModPrefix(i) ) ) )

 

Thank you @Chris Kuip !

 

I forgot to mention that this variable Q is time-dependent, i.e. it is associated with an index “t”. If I use

netoutflow =
    ScalarValue(
        StringToElement(
            AllIdentifiers,
            formatString( "%s::Q(t)", ModPrefix(i) ) ) )

then I do not get an error but it does not seem to work either, since the variables Q do not appear in the Math Program Inspector. Apparently, they are not added to the model at all. Do you know why?

 

Hi Sebastian,

 

You will need to create runtime identifiers, and the identifiers should be of type constraint.
Please check out:

  1. Language to create runtime identifiers - https://documentation.aimms.com/language-reference/advanced-language-components/model-structure-and-modules/runtime-libraries-and-the-model-edit-functions.html
  2. Procedure and functions that you can use - https://documentation.aimms.com/functionreference/model-handling/model-edit-functions/index.html
  3. An example that creates runtime identifiers of type constraint - https://how-to.aimms.com/Articles/131/131-Formulas-as-Data.html 

With kind regards,

Chris

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