Packages

Declarations may be stored in a package: once compiled, the package can be used by any model by means of the uses statement. Except for its beginning and termination (keyword model is replaced by package) a package source is similar to a normal model source. The following points should be noticed:

• all statements and declarations outside procedure or function definitions are used as an initialization routine: they are automatically executed before statements of the model using the package;
• symbols that should be published by the package must be made explicitly public using the public qualifier (see Section The public qualifier);
• parameters of a package are automatically added to the list of parameters of the model using the package;
• as opposed to modules that are dynamically linked, bim files of packages are used only at compilation time — they are not required for execution;
• a package cannot be imported several times by a model and packages publish symbols of packages they use. For instance, assuming package P1 imports package P2, a model using P1 cannot import explicitly P2 (with a uses statement) but has access to the functionality of P2 via P1.

The requirements block

Requirements are symbols a package requires for its processing but does not define. These required symbols are declared in requirement blocks which are a special kind of declaration blocks in which constants are not allowed but procedure/functions can be declared. The symbols of such a block have to be defined when the model using the package is compiled: the definitions may appear either in the model or in another package but cannot come from a module. Several packages used by a given model may have the same requirements (i.e. same identifier and same declaration). It is also worth noting that a package inherits the requirements of the packages it uses.

requirements
  an_int:integer
  s0: set of string
  bigar: array(S0) of real
  procedure doit(i:integer)
end-requirements