Trick for optional arguments with defaults

[hkvzjal]

@PierU

A way to prevent such an error is to use an ASSOCIATE block that spans the whole routine:

subroutine bar(...,a)
    real, intent(in), optional :: a
    real :: a_local
    a_local = 2.0; if (present(a)) a_local = a
    ASSOCIATE( a => a_local )
    ... ! "a" can now be safely used as an alias to a_local
    END ASSOCIATE
end subroutine

Be wary though of possible performance penalties that can be unadvertely introduced due to the way some compilers interpret associate Fortran skill markdown for codex - #22 by ivanpribec it probably won’t be an issue for scalar optionals but it could if the optional is an array.