Lahey/GNU Fortran

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8.254 UNPACK — Unpack an array of rank one into an array

Description:
Store the elements of VECTOR in an array of higher rank.
Standard:
Fortran 95 and later
Class:
Transformational function
Syntax:
RESULT = UNPACK(VECTOR, MASK, FIELD)
Arguments:

VECTOR Shall be an array of any type and rank one. It shall have at least as many elements as MASK has TRUE values.
MASK Shall be an array of type LOGICAL.
FIELD Shall be of the same type as VECTOR and have the same shape as MASK.

Return value:
The resulting array corresponds to FIELD with TRUE elements of MASK replaced by values from VECTOR in array element order.
Example:
          PROGRAM test_unpack
            integer :: vector(2)  = (/1,1/)
            logical :: mask(4)  = (/ .TRUE., .FALSE., .FALSE., .TRUE. /)
            integer :: field(2,2) = 0, unity(2,2)
          
            ! result: unity matrix
            unity = unpack(vector, reshape(mask, (/2,2/)), field)
          END PROGRAM
     

See also:
PACK, SPREAD