Add support for if-equations

[AnHeuermann]

Description

If-equations are not handled by the parser to convert Base Modelica to Modeling Toolkit models.

How to reproduce

Example 1: Simple If expression

IfEquation.mo

package 'IfEquation'
  model 'IfEquation'
    Real 'x';
  equation
    if time < 0.5 then
      'x' = 1.0;
    elseif true then
      'x' = 2.0;
    end if;
  end 'IfEquation';
end 'IfEquation';

julia> BaseModelica.parse_basemodelica("IfEquation.mo")
ERROR: MethodError: no method matching eval_AST(::BaseModelica.BaseModelicaIfEquation)
The function `eval_AST` exists, but no method is defined for this combination of argument types.

Closest candidates are:
  eval_AST(::BaseModelica.BaseModelicaPackage)
   @ BaseModelica ~/.julia/packages/BaseModelica/qCG6a/src/evaluator.jl:130
  eval_AST(::BaseModelica.BaseModelicaAnyEquation)
   @ BaseModelica ~/.julia/packages/BaseModelica/qCG6a/src/evaluator.jl:45
  eval_AST(::BaseModelica.BaseModelicaFunctionCall)
   @ BaseModelica ~/.julia/packages/BaseModelica/qCG6a/src/evaluator.jl:140
  ...

Stacktrace:
  [1] eval_AST(eq::BaseModelica.BaseModelicaSimpleEquation)
    @ BaseModelica ~/.julia/packages/BaseModelica/qCG6a/src/evaluator.jl:52
  [2] eval_AST(eq::BaseModelica.BaseModelicaAnyEquation)
    @ BaseModelica ~/.julia/packages/BaseModelica/qCG6a/src/evaluator.jl:46
  [3] (::BaseModelica.var"#15#17")(eq::BaseModelica.BaseModelicaAnyEquation)
    @ BaseModelica ./none:0
  [4] iterate
    @ ./generator.jl:48 [inlined]
  [5] collect(itr::Base.Generator{Vector{Any}, BaseModelica.var"#15#17"})
    @ Base ./array.jl:791
  [6] eval_AST(model::BaseModelica.BaseModelicaModel)
    @ BaseModelica ~/.julia/packages/BaseModelica/qCG6a/src/evaluator.jl:104
  [7] eval_AST(package::BaseModelica.BaseModelicaPackage)
    @ BaseModelica ~/.julia/packages/BaseModelica/qCG6a/src/evaluator.jl:132
  [8] baseModelica_to_ModelingToolkit
    @ ~/.julia/packages/BaseModelica/qCG6a/src/evaluator.jl:153 [inlined]
  [9] parse_basemodelica(filename::String)
    @ BaseModelica ~/.julia/packages/BaseModelica/qCG6a/src/BaseModelica.jl:23
 [10] top-level scope
    @ REPL[2]:1

Example 2: Nested inline if

package 'IfElseIfEquation'
  model 'IfElseIfEquation'
    Real 'x';
  equation
    if time < 0.33 then
      'x' = 1.0;
    elseif time < 0.66 then
      'x' = 2.0;
    else
      'x' = 3.0;
    end if;
  end 'IfElseIfEquation';
end 'IfElseIfEquation';

julia> BaseModelica.parse_basemodelica("IfElseIfEquation.mo")
ERROR: MethodError: no method matching eval_AST(::BaseModelica.BaseModelicaIfEquation)
The function `eval_AST` exists, but no method is defined for this combination of argument types.

Closest candidates are:
  eval_AST(::BaseModelica.BaseModelicaPackage)
   @ BaseModelica ~/.julia/packages/BaseModelica/qCG6a/src/evaluator.jl:130
  eval_AST(::BaseModelica.BaseModelicaAnyEquation)
   @ BaseModelica ~/.julia/packages/BaseModelica/qCG6a/src/evaluator.jl:45
  eval_AST(::BaseModelica.BaseModelicaFunctionCall)
   @ BaseModelica ~/.julia/packages/BaseModelica/qCG6a/src/evaluator.jl:140
  ...

Stacktrace:
  [1] eval_AST(eq::BaseModelica.BaseModelicaSimpleEquation)
    @ BaseModelica ~/.julia/packages/BaseModelica/qCG6a/src/evaluator.jl:52
  [2] eval_AST(eq::BaseModelica.BaseModelicaAnyEquation)
    @ BaseModelica ~/.julia/packages/BaseModelica/qCG6a/src/evaluator.jl:46
  [3] (::BaseModelica.var"#15#17")(eq::BaseModelica.BaseModelicaAnyEquation)
    @ BaseModelica ./none:0
  [4] iterate
    @ ./generator.jl:48 [inlined]
  [5] collect(itr::Base.Generator{Vector{Any}, BaseModelica.var"#15#17"})
    @ Base ./array.jl:791
  [6] eval_AST(model::BaseModelica.BaseModelicaModel)
    @ BaseModelica ~/.julia/packages/BaseModelica/qCG6a/src/evaluator.jl:104
  [7] eval_AST(package::BaseModelica.BaseModelicaPackage)
    @ BaseModelica ~/.julia/packages/BaseModelica/qCG6a/src/evaluator.jl:132
  [8] baseModelica_to_ModelingToolkit
    @ ~/.julia/packages/BaseModelica/qCG6a/src/evaluator.jl:153 [inlined]
  [9] parse_basemodelica(filename::String)
    @ BaseModelica ~/.julia/packages/BaseModelica/qCG6a/src/BaseModelica.jl:23
 [10] top-level scope
    @ REPL[7]:1

Example 3: No else case

I'm not sure if the following model is correct Base Modelica, but the parser get's stuck when havong no else:

package 'NoElse'
  model 'NoElse'
    Real 'x';
  equation
    if time < 0.33 then
      'x' = 1.0;
    elseif time < 0.66 then
      'x' = 2.0;
    elseif true then
      'x' = 3.0;
    end if;
  end 'NoElse';
end 'NoElse';

julia> BaseModelica.parse_basemodelica("NoElse.mo")

Versions 'n Stuff

• Julia Version 1.11.6
• BaseModelica v1.1.0
• OS: Ubuntu 24.04.3 LTS