Fortran Blog Post

debt-prioritizer.f95

program debt_prioritizer
  implicit none

  type debtor
      character(len=:), allocatable :: name
      integer       :: debt
  end type debtor

  ! Ugh! Global variables!?
  ! Originally, I was passing the "debtors" and "debtor_count"
  ! variables as parameters to all the subroutines and functions.
  type(debtor), dimension(:), allocatable :: debtors
  integer                                 :: debtor_count = 0

  call assign_values_to_globals()
  call prioritize_debt()
contains
  ! Assigns values to the global variables declared at the start of the
  ! program.
  subroutine assign_values_to_globals()
      call assign_debtor_count(debtor_count)
      allocate(debtors(debtor_count))
      call assign_debtors()
  end subroutine assign_values_to_globals

  ! Loops through the file to determine how many people owe money.
  ! I know this seems stupid to open the file twice, but I
  ! couldn't find a way to dynamically allocate items to an array
  ! that I could actually understand.
  subroutine assign_debtor_count(debtor_count)
      integer :: debtor_count, read_status, sum_of_lines = 0

      ! Open the input data file for reading:
      open(10, file = "input.txt", status = "old", action = "read")

      ! Loop through each line in the file to get a running count:
      do
          ! The "iostat" is used for error handling. If there's nothing to
          ! read, it throws an error (which is just a number other than 0).
          ! We don't want it to throw an error though, because it just hit
          ! the end of the file.
          read(10, *, iostat = read_status)
          if (read_status /= 0) exit

          sum_of_lines = (sum_of_lines + 1)
      end do

      ! If you don't do this, you end up with a crazy big number:
      close(10)

      debtor_count = sum_of_lines
  end subroutine assign_debtor_count

  ! Opens the input file, loops through the records, and populates the
  ! debtors array with the name and debt of the corresponding debtor.
  subroutine assign_debtors()
      character(50) :: line, name
      integer       :: read_status, debt, line_number = 1

      ! Open the input data file for reading:
      open(10, file = "input.txt", status = "old", action = "read")

      ! Loop through each line in the file to get the name and debt:
      do
          read(10, "(A)", iostat = read_status) line

          ! Exit the loop at the end of the file:
          if (read_status /= 0) exit

          ! Populate the name and debt variables with the value
          ! from the input file:
          call get_name_and_debt(line, name, debt)
          debtors(line_number)%name = name
          debtors(line_number)%debt = debt

          ! There needs to be an iterator to assign to each debtor:
          line_number = (line_number + 1)
      end do

      close(10)
  end subroutine assign_debtors

  ! Once the debtors are loaded into the array and their debt is calculated,
  ! this reorders them descending by debt (so whoever owes the
  ! most money is right at the top of the list). Once that's done, the
  ! debtors are written to a CSV file for easy parsing!
  subroutine prioritize_debt()
      call sort_descending_by_debt()
      call write_debtors_to_file()
      print *, "Done!"
  end subroutine prioritize_debt

  ! Splits the value of the line into the person's name and their
  ! corresponding debt.
  subroutine get_name_and_debt(line, name, debt)
      ! The name and debt in the input file are separated by a pipe:
      character(1) :: DELIM = "|"
      character(50) :: line, name, debt_string
      integer       :: debt, index

      ! Get rid of any whitespace at the end of the line:
      line = trim(line)

      ! Get the position of the pipe character:
      index = scan(line, DELIM)

      ! Pull the name from the line, essentially this grabs the line value
      ! from the first character of the line to where the pipe character was
      ! found in the "scan" function above:
      name = line(1 : index - 1)

      ! Pull the debt from the line, this just grabs the line value from the
      ! first character after the pipe until the end of the line:
      debt_string = line(index + 1 : )

      ! Convert the debt to a number. Character strings are
      ! considered to be "internal files" in Fortran.
      ! See https://www.eng-tips.com/viewthread.cfm?qid=37205
      read(debt_string, '(I5)') debt
  end subroutine get_name_and_debt

  ! This is a ridiculously inefficient bubble sort. It loops through each
  ! record, and within that loop it does another loop The higher debt
  ! amount is moved before the lower debt amount. This has to be done for
  ! each record, which is why there are 2 loops.
  subroutine sort_descending_by_debt()
      integer :: base_index, compare_index

      ! This loop starts at the beginning of the list and iterates by 1:
      do base_index = 1, debtor_count
          ! This loops through each record in the file (starting from the
          ! bottom of the list), looks at the value of the debt, and either
          ! leaves it in it's current position (if lower than the parent
          ! value) or moves it after the parent value:
          do compare_index = debtor_count, (base_index + 1), -1
              call swap(debtors(compare_index - 1), debtors(compare_index))
          end do
      end do
  end subroutine sort_descending_by_debt

  ! Given two debtors, this reorders them descending by debt level. If the
  ! larger debt value is on the left side, it doesn't do anything.
  subroutine swap(left_debtor, right_debtor)
      type(debtor) :: left_debtor, right_debtor, temp

      if (left_debtor%debt < right_debtor%debt) then
          temp = right_debtor
          right_debtor = left_debtor
          left_debtor = temp
      end if
  end subroutine swap

  ! If the CSV file "output.csv" doesn't already exist, it creates it in the
  ! same directory where you compiled the program. Once the file exists, it
  ! writes each debtor to the file.
  subroutine write_debtors_to_file()
      character(len=:), allocatable :: name_trimmed
      integer                       :: debtor_number

      print *, "Creating the output file..."
      open(20, file = "output.csv", action = "write")

      ! This just writes the first line headers so when you copy it into
      ! your spreadsheet software, you know what the columns represent:
      write (20, "(A)") "Name,Debt"

      do i = 1, debtor_count
          ! Get rid of any extra whitespace in the name:
          name_trimmed = trim(debtors(i)%name)

          print *, debtors(i)%debt

          ! Write the name and debt (separated by a comma) to the output file:
          write (20, 2000) name_trimmed, ",", debtors(i)%debt
          2000 format (A, A1, I5)
      end do

      close(20)
  end subroutine write_debtors_to_file
end program debt_prioritizer

input.txt

Vivian Larson|5458
Geraldine Gibson|9207
Violet Price|9745
Hilda Cohen|6835
Aurora Cooke|6463
Xyla Buck|6613
Cynthia Boone|5324
Gavin Russell|7419
Macey Guerra|6840
Chava Riley|7560
Cullen Sweeney|8156
Juliet Tate|8165
Latifah Cruz|7644
Murphy Hurst|9111
Moses Mccullough|7610
Cora Fowler|9864
Eaton Mcleod|6362
Cailin Day|6087
Aiko Mcconnell|8973
Hadley Finley|6365
Germaine Frost|5493
Kasper Michael|9897
Karyn Powers|6116
Kaitlin Flores|5452
Noel Carter|8507
Uriel Malone|8858
Dorian Leblanc|6067
Stuart Velazquez|6331
Gray Short|7475
Robin Kidd|9952
Charde Gould|8891
Burton Pace|6303
Nolan Carroll|7281
Iliana May|5394
Jemima Mcleod|9849
Britanni Fox|6977
Quintessa Medina|7487
William Levine|7455
Raven Cline|8283
Laura Mcleod|8112
Maile Bender|9466
Cecilia Jacobs|8880
Rigel Glover|6103
Jemima Hicks|6340
Zenaida Hernandez|7805
Taylor Boone|7903
Karen Greer|9100
Sonya Gutierrez|9362
Hope Chavez|7528
Penelope Bruce|5913
Juliet Simpson|7941
Jordan Thomas|6787
Kaitlin Clemons|9153
Harlan Holmes|9713
Byron Bruce|7589
Tatyana Barlow|6634
Jack Vinson|5186
Lael Jacobs|6404
Cade Torres|5912
Prescott Pratt|8818
Clinton Preston|8566
Eric Benson|6643
Quentin Dickson|5094
Quinn Buckley|5393
Peter Osborne|9609
Yvonne Brady|6522
Britanni House|5209
Mollie Wilkins|8641
Abbot Levine|6946
Kermit Mason|9265
Alden Burton|8833
Leigh Mccarthy|5827
Camilla Knox|6294
Sebastian Meyer|9540
Yuri Orr|6439
Dana Hamilton|6283
Dale Byrd|7308
Clarke Davenport|6025
Tiger Ball|7977
Kirk Sutton|6377
Briar Joseph|9827
Cailin Forbes|9618
Jolene Lucas|8298
Chava Chapman|7734
Kendall Noel|6634
Joelle Dillon|5445
Kevin Stephens|5321
Adena Hicks|6999
Stephanie Robinson|5302
Damian Snyder|7827
Tiger Cummings|5317
Colorado Irwin|9379
Ainsley Lynn|6267
Madison Trevino|9624
Lara Mcclure|7267
Hyatt Bailey|5752
Allegra Spence|9736
Kiara Jarvis|5591
Ignatius Martinez|7784
Griffin Hernandez|5046
Reagan Hebert|8326
Brent Aguirre|7258
Mason Wallace|8317
Willow Slater|5811
Katell Blake|9912
Shea Bowers|6002
Germaine Preston|8446
Zenia Hood|5401
Lois Sullivan|5505
Stewart Stein|7980
Odessa Ochoa|5677
Vera Bridges|6021
Whoopi Trevino|6544
TaShya Kane|7068
Jessica Snyder|6005
Fuller Sawyer|6544
Rafael Mason|7123
Miranda Lawrence|9441
Belle Meadows|5640
Kameko Atkins|5541
Philip Maldonado|6669
Kelly Garcia|7895
Guinevere Vang|5186
Shelly Huber|5249
Camilla Parrish|5649
Orli Cruz|8340
Neil Little|9715
Clark Matthews|6308
Allegra Garrison|6794
Martha Nelson|6244
Allegra Sherman|6536
Bryar Blevins|9412
Bo Davis|6928
Cheyenne Harmon|7016
Hadley Shaffer|6666
Fletcher Cooper|5799
Jason Scott|6288
Cade Wade|6009
Indira Poole|9814
Darius Lott|9193
Griffith Cherry|8623
Ulysses Meyers|7187
Lavinia Pickett|6813
Fatima Olson|7514
Abel Mccoy|5044
Fritz Lindsay|5941
Kameko Bartlett|7659
Hedwig Potts|5598
Shellie Ford|8867
Conan Peterson|7243
Joelle Daniels|9162
Dahlia Whitley|8846
Fritz Morrow|9178
Alika Melendez|9180
Todd French|9919
Carol Marshall|7270
Gannon Goff|9672
Orla Travis|5880
Maggy Tran|5488
Nomlanga Trevino|8328
Xavier Valencia|5278
Deacon Browning|6567
Merrill Sexton|6224
Paula Phillips|6805
Barclay Vang|6928
Jeremy Hull|9969
Nero Mercer|6568
Bertha Wooten|6251
Dean Mcfarland|5765
Brock Contreras|9212
Ella Blanchard|6069
Portia Holden|9001
Sebastian Russell|5123
Leo Nieves|7009
Harrison Rocha|6395
Hanae Goodman|7924
Ishmael Guy|8235
Breanna Knox|5174
Kylee Miranda|6824
Hadassah Mcpherson|9566
Vielka Cole|7238
Ashton Hatfield|8251
Hedda Reyes|5310
Dieter Sexton|5109
Lois Neal|8250
Allen Sanchez|9658
Christopher Hayden|6162
Caryn Delaney|8435
Eric Savage|6916
Wang Cooper|7518
Lacey Harvey|7535
Edward Frederick|6628
Quin Rocha|5464
Dane Snyder|6875
Jana Noel|5303
Heather Emerson|6247
Audra Rodgers|9548
Althea Church|7357
Shelly Moses|8397
Ursa Pratt|6427