dap4/d4core/src/main/java/dap4/core/ce/CEConstraint.java
protected int
    expansionCount(DapStructure struct)
    {
        int count = 0;
        for(DapVariable field : struct.getFields()) {
            if(findVariableIndex(field) >= 0) count++;
        }
        return count;
    }
protected int
    expansionCount(DapStructure struct)
    {
        int count = 0;
        for(DapVariable field : struct.getFields()) {
            if(findVariableIndex(field) >= 0) count++;
        }
        return count;
    }
Count the number of fields of a structure that
already in this view.

@param struct the dapstructure to check
@return # of fields in this view
@throws DapException