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Structure Check

Language Namespace: de.itemis.mps.structurecheck

The statement check structure of can check the structure of a node. The statement throws a runtime exception when the check fails. It supports a few different checkers. The expression thisElement always refers to the current element:

  • composite checker combines multiple checks.
  • condition checks that a boolean condition is true.
  • element checks that one or multiple elements of the same structure match. The default cardinality is one (x1) which you can set to a different value.
  • property checks a property of the element. It compares the left expression to the right expression.
  • sequence checks that a sequence of elements matches the listed elements. To match the ordering of the declared elements, set the ordered flag (set to unordered otherwise). 4 supported checker types are available:
    • all elements must match the declared elements (exactly),
    • all elements must match, but there can be more elements (allOrMore)
    • all elements must match, but there can be fewer elements (allOrLess)
    • none of the elements should match (noneOfThese).
Example: check the structure of an ArrayList
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list<Object> root = new arraylist<Object>{"a", 2, new arraylist<Integer>{10, 20}, 3}; 

check structure of root { 
  sequence thisElement contains unordered allOrMore { 
    element x1 of type Integer { 
      property 2 = thisElement 
    } 
    element x1 of type string { 
      condition thisElement != null   
      property "a" = thisElement 
    } 
    element x1 of type list<Integer> { 
      sequence thisElement contains ordered exactly { 
        element x1 of type <no subtype> { 
          property 10 = thisElement 
        } 
        element x1 of type <no subtype> { 
          property 20 = thisElement 
        } 
      } 
    } 
  } 
};