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Manual Reference Pages  - return (7fortran)

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NAME

return(7f) - [STATEMENT] completes execution of the instance of the subprogram in which it appears

SYNOPSIS

RETURN [scalar-int-expr]

DESCRIPTION

Execution of the RETURN statement completes execution of the instance of the subprogram in which it appears.

It is generally considered good practice to avoid having multiple RETURN statements in a single subprogram. A RETURN is not required in a subprogram as reaching the end of the subprogram is equivalent to execution of a RETURN statement with no expression.

The RETURN statement must appear in the scoping unit of a function or subroutine subprogram.

OPTIONS

scalar-int-expr Alternate returns are deprecated!

                    If the expression appears and has a value n between
                    1 and the number of asterisks in the dummy argument
                    list, the CALL statement that invoked the subroutine
                    transfers control to the statement identified by
                    the nth alternate return specifier in the actual
                    argument list of the referenced procedure. If the
                    expression is omitted or has a value outside the
                    required range, there is no transfer of control to
                    an alternate return.

                    The scalar-int-expr is allowed only in the scoping
                    unit of a subroutine subprogram.

EXAMPLE

Sample program

        program demo_return
           call tryreturn(1)
           write(*,*)’back at main program:1’
           call tryreturn(10)
           write(*,*)’back at main program:10’
        contains
        subroutine tryreturn(i)
        integer,intent(in) :: i
           select case(i)
           case(1)
              write(*,*)’*one*’
              return
           case(2)
              write(*,*)’*two*’
              return
           case default
              write(*,*)’*unexpected value*’
           end select
           write(*,*)’*<ERROR> should not get here*’
        end subroutine tryreturn
        end program demo_return

Results:

     >  *one*
     >  back at main program:1
     >  *unexpected value*
     >  *<ERROR> should not get here*
     >  back at main program:10

Sample program using alternate returns. Alternate returns are an obsolescent feature.

       program alt_return
       implicit none
          call one(2,*10,*20,*30)
          write(*,*)’did not select alternate return’
          goto 999
       10 continue
          write(*,*)’picked first alternate return’
          goto 999
       20 continue
          write(*,*)’picked second alternate return’
          goto 999
       30 continue
          write(*,*)’picked third alternate return’
          goto 999
       999 continue
       contains
       subroutine one(ipick,*,*,*)
       implicit none
       integer :: ipick
          select case(ipick)
           case(1)
             write(*,*)’first alternate return selected’
             return 1
           case(2)
             write(*,*)’second alternate return selected’
             return 2
           case(3)
             write(*,*)’third alternate return selected’
             return 3
          end select
          write(*,*)’no alternate return selected’
       end subroutine one
       end program alt_return

Results:

     >  second alternate return selected
     >  picked second alternate return

Fortran statement descriptions (license: MIT) @urbanjost

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Nemo Release 3.1

return (7fortran)

August 19, 2024

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