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| ☜ | ^$Y*Draft MDC Standard | ☞ | ||||
These ssvns are reserved for users and are called user-defined structured system variables. The syntax is
An implementation is required to provide a means of associating a routine with one or more specific user-defined structured system variables.
This routine is called whenever a reference is made to a user-defined structured system variable by calling one of the following labels in the routine with first the parameter being the value of $NAme of the reference and the second parameter, if any, as below:
| Reference Type | Label | Second Parameter | Result |
| Evaluation | %VALUE | Yes | |
| $Data parameter | %DATA | Yes | |
| $Get parameter | %GET | Second parameter of $Get | Yes |
| $Order paramater | %ORDER | Second parameter of $Order | Yes |
| $Query parameter | %QUERY | Second parameter of $Query | Yes |
| Kill command | %KILL | No | |
| KSubscripts command | %KSUBSCRIPTS | No | |
| KValue command | %KVALUE | No | |
| Merge command target | %MERGE | Source glvn | No |
| Merge command source | %MERGES | Target glvn | No |
| Value assignment | %SET | Value to be assigned | No |
The usage of $Order and $Query with unsubscripted user-defined system variables has the same effect as if they were not user defined.
| Editor’s note: This seems erroneous to me: $Query of an unsubscripted reference is no differrent from $Query of a subscripted reference, it just should return the namevalue of the first data node. I think it should not be labeled as an exception here. $Order of an unsubscripted reference is not defined in this standard. |
If both the source and target of a Merge command are user-defined structured system variables, then only the Merge label for the target ssvn is called.
Let r be the name of the routine being called when a reference is made to a certain user-defined structured system variable, and let l be the label at which this routine is called. If the routine does not exist when a reference is made to the user-defined structured system variable, then an error condition occurs with ecode = M97. If the routine exists, but the label does not exist when a reference is made to the user-defined structured system variable, then an error condition occurs with ecode = M13.
Note: names of user-defined structured system variables which differ only in the use of corresponding upper and lower case letters are not equivalent.
Note: Users providing routines to implement user-defined structured system variables are responsible for ensuring that other side-effects (such as a change to $Test or $Data values), which would not have taken place, had the reference been to a global variable, do not occur as a result of calling the routine.
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Copyright © Standard Documents; 1977-2024 MUMPS Development Committee;
Copyright © Examples: 1995-2024 Ed de Moel;
Copyright © Annotations: 2003-2008 Jacquard Systems Research
Copyright © Annotations: 2008-2024 Ed de Moel.
Some specifications are "approved for inclusion in a future standard". Note that the MUMPS Development Committee cannot guarantee that such future standards will indeed be published.
This page most recently updated on 15-Nov-2023, 12:06:44.
For comments, contact Ed de Moel (demoel@jacquardsystems.com)