[Moradi]

Hi,
I am doing coding. I use Fortran95.
I have some subroutines which contains optional arguments.
When I call them I can use "if () then" or "select case()" to choose whether assign data to these optional arguments or not. As I know even if I assign an undefined data (undefined array; e.g. an allocatable array which i not allocated) to these subroutines, program will not encounter any problem.
My question is: should I actually use a criterion (using "if" or "select case") when I assign data to these subroutines (for example: when I have an allocatable array I can use "if"; so, when the array is not allocated I will not assign it to the optional argument. But, is it necessary)?

Thanks so much.

[ztdep]

generally, we set it to a default value ,such as 0 to avoid some zero.

[Moradi]

Originally Posted by ztdep

generally, we set it to a default value ,such as 0 to avoid some zero.

First of all, thanks for giving me some comments.
Yes, that is right. But, what if this variable (an array) is not allocated (if I can ignore allocation of an unnecessary array , I can save the memory[assume I am solving for laminnar flow. So, alocation of turbulence related variables will be unnecessary]). My question actually is about such cases.
Thanks so much Ztdep

[ztdep]

if(Solve Turbulent) then
Allocate( Turbulent related variables )
Else
Allocate( laminar flow related variables
endif