L5 : argument INTENT
********************

All arguments to routines shall be declared with an INTENT.

* ``INTENT(IN)`` : variables which are not assigned to in the scope 
* ``INTENT(OUT)`` : variables whose previous content is irrelevant, and which are written to in the scope
* ``INTENT(INOUT)`` : all other variables

*warning*
Particular care should be paid to intent of array variables:
* arrays where only a few locations are updated but other locations 
contain required values, *must* be declared as INTENT(INOUT)

* arguments declared as allocatable may be deallocated at entry if declared as INTENT(OUT)