For some reason, and only in certain cases, the built-in
preprocessor of ifort cannot handle constructs such as

  #define FOO bar

  print *, "foo&
  &FOO&
  &baz"

or more specifically

  #define DATATYPE double

  print *, some_&
  &DATATYPE&
  &_routine

which, however, are quite handy. GCC seems to handle those as
expected.