Next: , Previous: , Up: Well-formedness – System   [Contents][Index]

11.12.8 System composition is recursive

A system may instantiate an arbitrary set of components, which in turn can be systems themselves. It is not allowed to have a self-instance neither directly nor indirectly, since that would lead to an infinite tree of components.

In the example below five systems are defined that have mutual instances. System c1 instantiates c3, which instantiates c4, which instantiates c1. 

component c1 {
  system {
    c2 ci2;
    c3 ci3;
  }
}

component c2 {
  system {
    c5 ci5;
  }
}

component c3 {
  system {
    c4 ci4;
    c2 ci2;
  }
}

component c4 {
  system {
    c1 ci1;
  }
}

component c5 {
  system { } // an empty system
}

This results in the following error messages: 

recursive-system.dzn:1:1: error: system composition of `c1' is recursive
recursive-system.dzn:14:1: error: system composition of `c3' is
    recursive
recursive-system.dzn:21:1: error: system composition of `c4' is
    recursive