It is one of the three main components of the Data Provider output-based declarative language.
Sometimes it is necessary to make internal calculations that do not necessarily have to go into the Output itself. Variables are used in this case, in a Data Provider Group statement.
&var = <Formula>
View Syntax conventions
Is the name of the variable.
Is a conditional Formula (horizontal as well as aggregate or Compound). That is, it could be several conditional expressions. This includes either an isolate attribute, or an invocation to a procedure with output or a Data Provider, a constant, as well as the typical formulas.
&TotalCustomers = 0
CustomerId = CustomerId
CustomerName = CustomerName
&TotalCustomers = &TotalCustomers + 1
Total = &TotalCustomers