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|  | //destination// | **:=:** | //source// |

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| //destination// | The label of a GROUP, RECORD, or QUEUE data structure, or an array. |
| //source// | The label of a GROUP, RECORD, or QUEUE data structure, or a numeric or string constant, variable, procedure, or expression. |

The** :=:** sign executes a deep assignment statement which performs multiple individual component variable assignments from one data structure to another. The assignments are only performed between the variables within each structure that have exactly matching labels, ignoring all prefixes. The compiler looks within nested GROUP structures to find matching labels. Any variable in the //destination// which does not have a label exactly matching a variable in the //source//, is not changed.

Deep assignments are performed just as if each matching variable were individually assigned to its matching variable. This means that all normal data conversion rules apply to each matching variable assignment. For example, the label of a nested //source// GROUP may match a nested //destination// GROUP or simple variable. In this case, the nested //source// GROUP is assigned to the //destination// as a STRING, just as normal GROUP assignment is handled.

The name of a //source// array may match a //destination// array. In this case, each element of the //source// array is assigned to its corresponding element in the //destination// array. If the //source// array has more or fewer elements than the //destination// array, only the matching elements are assigned to the //destination//.

If the //destination// is an array variable that is not part of a GROUP, RECORD, or QUEUE, and the //source// is a constant, variable, or expression, then each element of the //destination// array is initialized to the value of the //source//. This is a much more efficient method of initializing an array to a specific value than using a LOOP structure and assigning each element in turn.

The //destination// or //source// may also name a CLASS structure, which, in this case, will be treated as a GROUP. However, if you do so, you violate the concept of encapsulation, since deep assignment is a structure piercing operation. Therefore, it is not recommended.

Finally, whenever possible is it always more efficient to use a direct assignment of two matching structures in lieu of deep assignments.

**Example:**
<code>
Group1 GROUP
S       SHORT
L       LONG
       END

Group2 GROUP
L       SHORT
S       REAL
T       LONG
       END

ArrayField SHORT,DIM(1000)
 CODE
 Group2 :=: Group1    !Is equivalent to: 
                      !Group2.S = Group1.S
                      !Group2.L = Group1.L
                      !and performs all necessary data conversion 
 ArrayField :=: 7     !Is equivalent to: 
                      !LOOP I# = 1 to 1000
                      ! ArrayField[I#] = 7
                      !END
</code>
**See Also:**

[[group  compound data structure .htm|GROUP]]

[[record  declare record structure .htm|RECORD]]

[[queue  declare a memory queue structure .htm|QUEUE]]

[[dim  set array dimensions .htm|DIM]]