Data-types and Expressions
Identifiers are names that are used in a template and can represent constants, variables or parameters. The differences between these are noted here:
● Constants are identifiers whose values are constant and cannot be changed in DGL statements.
● Variables are identifiers whose values can change in DGL statements.
●Before you use an identifier, you must declare whether it is a constant, variable or parameter. Furthermore, you must declare the particular type of value that can be assigned to the identifier; we call this type a data-type.
For instance, an identifier (whether constant, variable, or parameter) may be declared to hold integer values, float values, string values, etc.
Identifiers can be combined to construct expressions; these can be used in various kinds of statements and database extraction functions. Various kinds of expressions can be constructed, depending on the data-types of the identifiers of which they are constituted.
For instance, you may construct numeric or string expressions as well as Rational Statemate element expressions.
This section deals with both data-types and the expressions you can construct from them. In addition, enumerated types; variables or return values of a function that take a restricted number of discrete values, are described.