pack function fortran sparse get index
ian@eris:~/work/stack$ cat pack.f90
Program pack_index
Implicit None
Integer, Dimension( 1:4 ) :: my_array = [ 160, 0, 230, 0 ]
Integer, Dimension( : ), Allocatable :: choices
Integer, Dimension( : ), Allocatable :: indices
Integer :: i
indices = Merge( 0, [ ( i, i = 1, Size( my_array ) ) ], my_array == 0 )
choices = Pack( indices, indices /= 0 )
Write( *, * ) choices
End Program pack_index
ian@eris:~/work/stack$ gfortran-8 -std=f2008 -fcheck=all pack.f90
ian@eris:~/work/stack$ ./a.out
1 3