Get the next requirement of a package.

Reference pointer for the next call to XPRMgetnextreq.

This function returns the next requirement of a package: requirements of a package are the symbols it declares but that must be defined by the model using it. The type returned by the function can be decoded in the same way as for a type returned by XPRMfindident. The information returned via the last argument depends on the type: for a scalar, a set or a list a NULL pointer is returned; for an array the list of the names of the indexing sets is returned through a text string (for instance the array a:array(S1,S2) has the following data string: "S1,S2"). In the case of a subroutine, an XPRMproc reference is provided: this can be used with XPRMgetprocinfo for getting information on the required routine. The second parameter is used to store the current location in the table of requirements; if this parameter is NULL, the first requirement of the table is returned. This function returns NULL if it is called with the reference to the last requirement defined by the given model. Otherwise, the returned value can be used as the input parameter ref to get the following requirement and so on.