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knownProblems.md

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Known problems

This document describes all current known problems with alfi.

General

  • Assignment Expressions for names that are not yet defined before (declaration by assignment)
  • Scoping for super invocation expression
    • -> Need classes for this
  • The NameBinding used in the FeatureReference should be turned into a MPS reference to a Namespace Member or something
    • -> Need classes for this
    • -> Probably also need a typesystem for that, to evaluate which type the expression on the left has

Generators

  • Sometimes Alf automatically converts to Real or something where as java would stay in Integer
    • Makes division operator behave differently
    • -> Easier to solve with a working typesystem
  • ALF Multiplicities need to be considered
    • Translate to Optional / List
    • -> Easier to solve with a working typesystem
  • In contrast to most other languages, Alf has no support/concept for overwriting/hiding (sub-)scopes inside a Statement List
    • See also ModelDriven/Alf-Reference-Implementation#103
    • Possible solution
      • For BlockStatments we solved this by just copying the contained statements into the outer statement list without creating a BlockStatement
      • For Conditions and Loops we need to define all variables (that are not already defined) before and in the body convert definitions to assignments
  • Support (in-)out Parameters
    • Possible solution
      • Use a container as the actual parameter (with a different name)
      • Define the variable in the beginning of the method (optionally initialize it)
      • Set the value of the container at the end of the method and before every return statement (from the defined variable)
      • Do respective packing and unpacking around invocations
  • Not Implemented in generators: Feature Invocation, Super Invocation, Instance Creation, Assignment_FeatureLeftHandSide, PropertyAccess, and so on once we have classes and a type system
    • [C# only] Super Constructor Invocation needs special care
  • Unbounded Values cannot be represented in other languages
    • -> Currently we throw an error if the generator encounters it in a place where it would need to be translated

Textgen

  • The Whitespace is not perfect in many places

Editor

None

TextGenGen (generating new TextGen from editor)

Stuff to do manually after running TextGenGen:

  • In EndOfLineComment at append \n ; as the last statement
  • In Package Definition delete append {<no body>} ;
    • This can be fixed by using fumapps newest version of TextGenGen and setting the cell id to some magic string
  • Add file extension to Unit: alf
  • Add file path to Unit:
list<String> names = new arraylist<String>;
if (node.model.name.isNotEmpty) {
  names.add(node.model.name);
}
if (node.getVirtualPackageName().isNotEmpty) {
  names.add(node.getVirtualPackageName());
}
return String.join(".", names);