Section Arrays: Enlarge Array

Adapted from: gjbex/Fortran-MOOC

This program demonstrates enlarging an array in Fortran.

program enlarge_array
  use, intrinsic :: iso_fortran_env, only : error_unit
  implicit none
  integer, parameter :: initial_size = 3, size_incr = 2
  integer, dimension(:), allocatable :: values
  integer :: i
  
  allocate (values(initial_size))
  
  do i = 1, size(values)
      values(i) = i
  end do
  print *, values

  do i = 1, 3
      call grow_array(values, size_incr)
      print *, values
  end do

  deallocate (values)

  do i = 1, 3
      call grow_array(values, size_incr)
      print *, values
  end do

  deallocate (values)

contains

    subroutine grow_array(values, size_incr)
        implicit none
        integer, dimension(:), allocatable, intent(inout) :: values
        integer, value ::size_incr
        integer, dimension(:), allocatable :: new_values
        integer :: i, size_of_values_array

        ! Added statement below to simplify allocate statement
        size_of_values_array = size(values)

        if (allocated(values)) then
            ! The below statement fails because values and new values are of different sizes
            ! seems to be a Fortran version issue
            !allocate (new_values(size_of_values_array + size_incr), source=values)
            allocate (new_values(size_of_values_array + size_incr))

            ! For now I will just copy values into new_values using a loop
            do i = 1, size(values)
                new_values(i) = values(i)
            end do

            do i = size(values) + 1, size(new_values)
                new_values(i) = i
            end do

            deallocate (values)
            
            call move_alloc(new_values, values)
        else
            allocate (values(size_incr))
            do i = 1, size(values)
                values(i) = i
            end do
        end if
    end subroutine grow_array

end program enlarge_array

The above program is compiled and run using Fortran Package Manager (fpm):

Build the Program using FPM (Fortran Package Manager)

import os
root_dir = os.getcwd()

code_dir = root_dir + "/" + "Fortran_Code/Section_Arrays_Enlarge_Array"

os.chdir(code_dir)

build_status = os.system("fpm build 2>/dev/null")

Run the Program using FPM (Fortran Package Manager)

exec_status = os.system("fpm run 2>/dev/null")

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