Intent (out)- the dummy argument may be set and then modified within the procedure, and the values returned to the caller. Intent (in) - the value of the dummy argument may be used, but not modified, within the procedure. The default is no intent checking - which can allow erroneous coding to be undetected by the compiler. When declaring variables inside functions and subroutines that need to be passed in or out, intent may be added to the declaration. Subroutine square_cube ( i, isquare, icube ) integer, intent ( in ) :: i ! input integer, intent ( out ) :: isquare, icube ! output isquare = i ** 2 icube = i ** 3 end subroutine program main implicit none external square_cube ! external subroutine integer :: isq, icub call square_cube ( 4, isq, icub ) print *, "i,i^2,i^3=", 4, isq, icub end program Intent The following program calls a function to compute the sum of the square and the cube of an integer. In Fortran, one can use a function to return a value or an array of values. A subroutine does not return a value, but can return many values via its arguments and can only be used as a stand-alone command (using the keyword call). A function must return a single value, and can be invoked from within expressions, like a write statement, inside an if declaration if (function) then, etc. Haskell) only allow functions, because subroutines can, in some case, modify input variables as side-effects, which can complicate the code.įunctions are simpler than subroutines. Pure functional programming languages (e.g. Many programming languages do not distinguish between functions and subroutines (e.g. call sub1 ( e, f ) ! Now e or f, or both (or neither) may be modified.
! sub1 performs some operation on input variables e and f. ! sub1 is a subroutine defined elsewhere.
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