program main_test
implicit none
real, dimension(5) :: arr1, arr2
LOGICAL, dimension(5) :: ad, ab, ac, tot
INTEGER , dimension(:), allocatable:: arr3
INTEGER :: i
arr1 = [1.0,2.3,-0.5,3.3,-1.6]
arr2 = [1.0,-5.3,-0.5,-3.0,-1.6]
ab = arr1 < 4
ad = arr1 > 2
ac = arr2 < 0
tot = ad .and. ab .and. ac
allocate(arr3(size(tot)))
arr3 = pack([(i,i=1,5)],tot)
print *, tot, 'size(tot)=', size(tot)
print *, 'indices:', arr3
print *, 'size:', size(arr3)
end program main_test
输出结果：
F T F T F size(tot)= 5
indices: 2 4
size: 2
动态数组会根据实际传递的数组大小调整动态数组大小。但是当声明静态数组arr3数组的大小为5的话，indices的输出结果会是这样的：
indices: 2 4 160 0 1211325946
后面3个数字应该是空的数组自动生成的元素。