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Description

The unpack procedure assigns values to some or all of the elements of an unpacked array by copying all of the elements of a packed array into the unpacked array. The elements of both arrays must have the same type.

Parameter

• The first parameter is a reference to the packed array variable that contains the array elements to copy.
• The second parameter is a reference to the unpacked array variable that contains the array elements to be copied into.
• The third parameter is an expression of ordinal type that specifies the start element of the unpacked array (i.e. the element of the unpacked array to start copying to). All of the elements of the unpacked array from the start element to the end are available to be copied into. It is an error if the number of elements in the unpacked array available to be copied into is less then the number of elements in the packed array, since all the elements in the packed array are copied. NOTE: This parameter must be assignment compatible with the index type of the unpacked array.

Suppose you have the following arrays

   p : packed array[21..23] of integer;
   u : array[51..60] of integer;

then

   unpack(p, u, 51)

copies elements 21 to 23 of p into elements 51 to 53 of u.

and

   unpack(p, u, 57)

copies elements 21 to 23 of p into elements 57 to 59 of u.

and

   unpack(p, u, 59)

produces an error since only two elements (i.e. 59 and 60) of u are available to be copied into but all three elements of p must be copied.

Portability

Operating Systems: All
Standard Pascal: Yes

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