Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!usc!sdd.hp.com!hplabs!hpfcso!acmeyer
From: acmeyer@hpfcso.HP.COM (Alan C. Meyer)
Newsgroups: comp.lang.fortran
Subject: Re: Keyword and optional argments (was Fortran vs C)
Message-ID: <9080009@hpfcso.HP.COM>
Date: 1 Dec 90 17:32:01 GMT
References: <MAINE.90Nov29200637@altair.dfrf.nasa.gov>
Organization: Hewlett-Packard, Fort Collins, CO, USA
Lines: 31

>I 100% agree.  And I note that this is incorporated in Fortran 90
>modules, one of my favorite Fortran 90 features.

To elaborate a little (and be a little picky?), keyword arguments can
be used in F90 for any procedure which has an "explicit interface".  In
F90, this means any intrinsic procedure, module procedure, or internal
procedure can always be invoked with keyword arguments.  In addition,
it also includes any external procedure for which an interface block is
accessible.

So, to build on the given example, an external procedure "read_the_file"
could also be called with keyword args like so -

	subroutine get_ready
	  ...
	interface
           subroutine read_the_file(file,format,some_other_argument,into)
	   use precision
           character, intent(in) :: file*(*)
           character, intent(in), optional :: format*(*)
           integer, intent(in), optional :: some_other_argument
           real(r_kind), intent(out) :: into
           end subroutine read_the_file
	end interface
	   ...
	call read_the_file(into=some_array, file='...')


Alan Meyer
Colorado Language Lab
Hewlett-Packard


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