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2.10.3 Cell Expressions (CellExpression)

Even less complicated than the definition of strings is the one of the so-called cell expressions. There does not exist a way to make up more complex expressions of simple ones at all! In consequence, all cell expressions we could ever think of are captured by the list below:

• cell constants (CellConstant)
• symbolic cell constants (CellConstantIdentifier)
• cell variables (CellVar)
• constructions of the form { RegExpressionList }
  
• neighbours (NeighbourIdentifier)

We will have a closer look to the kind of cell expressions given by

Here the contents of all registers RegExpression are indicated in an explicitely way. There must be as many RegExpression as registers declared before. Depending on the precise, predetermined state structure (number, order, and kind of registers) they can be integer expressions or string expressions respectively or VOID.
 

Note that the use of neighbours is only allowed in SDL, but not in RDL. For this reason CellExpression is used in RDL with a slightly different definition, without NeighbourIdentifier:
 

From time to time it makes sense to forbid neighbours as cell expressions in SDL as well; therefore, we consider there the class StrictCellExpression with exactly the same meaning as CellExpression in RDL.

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