Declaration of arguments and local identifiers

Specifying arguments

All (formal) arguments of a procedure or function must be specified as a parenthesized, comma-separated, list of non-indexed identifier names. All formal arguments must also be declared as local identifiers in a declaration section local to the procedure or function. These local declarations then specify the further domain and range information of the arguments. If an argument has not been declared when you create (or modify) a procedure or function, AIMMS will open the dialog box illustrated in Fig. 25 which helps you add the appropriate declaration quickly and easily.

Fig. 25 Argument Declaration dialog box

After completing the dialog box, AIMMS will automatically add a declaration section to the procedure or function, and add the arguments displayed in the dialog box to it, as illustrated in Fig. 24.

Input-output type

An important aspect of any argument is its input-output type, which can be specified by selecting one of the Input, InOut, Output or Optional properties in the Argument Declaration dialog box. The input- output type determines whether any data changes you make to the formal arguments are passed back to the actual arguments on leaving the procedure. The precise semantic meaning of each of these properties is discussed in the AIMMS Language Reference book.

Argument attributes

The choices made in the Argument Declaration dialog box are directly reflected in the attribute form of the local identifier added to the model tree by AIMMS. As an example, Fig. 26 shows the attribute form of the single argument mf of the procedure CheckComputableFlow added in Fig. 25.

In the dialog box of Fig. 25 it is not possible to modify the dimension of a procedure or function argument directly. If your procedure or function has a multidimensional argument, you can specify this with the IndexDomain attribute of the argument after the argument has been added as a local identifier to the model tree.

Fig. 26 Declaration form of a procedure argument

Prototype checking

For every call to the procedure or function, AIMMS will verify whether the types of all the actual arguments match the prototypes supplied for the formal arguments, including the supplied index domain and range. For full details about argument declaration refer to the AIMMS Language Reference book.

Local declarations

In addition to arguments, you can also add other local identifiers to declaration sections within procedures and functions. Such local identifiers are only known inside the function or procedure. They are convenient for storing temporary data that is only useful within the context of the procedure or function, and have no global meaning or interpretation.

Not all types supported

Not all identifier types can be declared as local identifiers of a procedure or function, because of the global implications they may have for the AIMMS execution engine. When you try to add a local identifier to a procedure or function, AIMMS will only offer those identifier types that are actually supported within a procedure or function. An example of an identifier type that cannot be declared locally is a constraint.

Not all attributes supported

In addition, for local identifiers, AIMMS may only support a subset of the attributes that are supported for global identifiers of the same type. For instance, AIMMS does not allow you to specify a Definition attribute for local sets and parameters. In the attribute window of local identifiers such non-supported attributes are automatically removed when you open the associated attribute form.