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Section Call By Semantics: Call By Value¶

Adapted from: https://github.com/gjbex/Fortran-MOOC/tree/master/source_code/call_by_semantics

This program demonstrates calling by value in Fortran.¶

program call_by_value
    implicit none
    integer :: n

    n = 5
    print *, n, "! = ", factorial(n)
    
    print *
    
    n = 6
    print *, n, "! = ", factorial(n)

contains

    function factorial(n) result(fac)
        implicit none
        integer, value :: n
        integer :: fac

        fac = 1
        do while (n > 1)
            fac = fac*n
            n = n - 1
        end do
    end function factorial

end program call_by_value

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_Call_By_Semantics_Call_By_Value"

%%capture
%%writefile section_call_by_semantics_call_by_value.f90
program call_by_value
    implicit none
    integer :: n

    n = 5
    print *, n, "! = ", factorial(n)
    
    print *
    
    n = 6
    print *, n, "! = ", factorial(n)

contains

    function factorial(n) result(fac)
        implicit none
        integer, value :: n
        integer :: fac

        fac = 1
        do while (n > 1)
            fac = fac*n
            n = n - 1
        end do
    end function factorial

end program call_by_value

!bat *.f90

───────┬────────────────────────────────────────────────────────────────────────
       │ File: section_call_by_semantics_call_by_value.f90
───────┼────────────────────────────────────────────────────────────────────────
   1   │ program call_by_value
   2   │     implicit none
   3   │     integer :: n
   4   │ 
   5   │     n = 5
   6   │     print *, n, "! = ", factorial(n)
   7   │     
   8   │     print *
   9   │     
  10   │     n = 6
  11   │     print *, n, "! = ", factorial(n)
  12   │ 
  13   │ contains
  14   │ 
  15   │     function factorial(n) result(fac)
  16   │         implicit none
  17   │         integer, value :: n
  18   │         integer :: fac
  19   │ 
  20   │         fac = 1
  21   │         do while (n > 1)
  22   │             fac = fac*n
  23   │             n = n - 1
  24   │         end do
  25   │     end function factorial
  26   │ 
  27   │ end program call_by_value
───────┴────────────────────────────────────────────────────────────────────────

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")

           5 ! =          120

           6 ! =          720