Merge two arrays.

$MERGE destination=source

The $MERGE statement is used to merge two arrays. $MERGE destination=source copies source into destination and all descendants of source into descendants of destination. It does not modify source, or kill any nodes in destination.

$MERGE simplifies the copying of a subtree (multiple subscripts) of a variable to another variable. Either variable can be a subscripted local variable, process-private global, or global. A subtree is all variables that are descendants of a specified variable.

If destination is undefined, $MERGE defines it and sets it to source. If source is undefined, $MERGE completes successfully, but does not change destination. When the destination and source are the same variable, no merge occurs. $MERGE issues an error if the source and destination have a parent-child relationship.

You can specify multiple, comma-separated destination=source pairs. They are evaluated in left-to-right order.

The $MERGE command can take longer than most other Caché MVBasic commands to execute. As a result, it is more prone to interruption. The effect of interruption is implementation-specific. Under Caché, an interruption may cause an unpredictable subset of the source to have been copied to the destination subtree.