Fortran 90 Presence Of Optional Arguments

Question

I do not understand the behavior of the present() intrinsic function with pgf90 7.2. I wrote a 20 line sample program to test this, but the results still make no sense to m

Answer 1

In Modern Fortran optional arguments must be declared as optional in the calling function (either through a module or an explicit interface). In Fortran 77 it was possible to simply leave out the last argument, if it was a scalar number, so optional arguments could be passed without extra declaration in the calling routine. This might not have been part of the Fortran standard, but it was a helpful feature provided by wise compiler implementations. Unfortunately, Modern Fortran killed this awesome feature.