* Fortran editing helpers for Emacs

** Overview

You write (or work on) large, modern fortran code bases.  These make
heavy use of function overloading and generic interfaces.  Your brain
is too small to remember what all the specialisers are called.
Therefore, your editor should help you.  This is an attempt to do
this for Emacs.

f90-interface-browser.el is a (simple-minded) parser of fortran that
understands a little about generic interfaces and derived types.

** External functions

- =f90-parse-interfaces-in-dir= :: Parse all the fortran files in a
     directory
- =f90-parse-all-interfaces= :: Parse all the fortran files in a
     directory and recursively in its subdirectories
- =f90-browse-interface-specialisers= :: Pop up a buffer showing all
     the specialisers for a particular generic interface (prompted
     for with completion)
- =f90-find-tag-interface= :: On a procedure call, show a list of the
     interfaces that match the (possibly typed) argument list.  If no
     interface is found, this falls back to =find-tag=.
- =f90-list-in-scope-vars= :: List all variables in local scope.  This
     just goes to the top of the current procedure and collects named
     variables, so it doesn't work with module or global scope
     variables or local procedures.
- =f90-show-type-definition= :: Pop up a buffer showing a derived type
     definition.

** Customisable variables

- =f90-file-extensions= :: A list of extensions that the parser will
     use to decide if a file is a fortran file.

** Details and caveats

The parser assumes you write fortran in the style espoused in Metcalf,
Reid and Cohen.  Particularly, variable declarations use a double
colon to separate the type from the name list.

Here's an example of a derived type definition:
#+BEGIN_SRC f90
type foo
   real, allocatable, dimension(:) :: a
   integer, pointer :: b, c(:)
   type(bar) :: d
end type foo
#+END_SRC

Here's a subroutine declaration:
#+BEGIN_SRC f90
subroutine foo(a, b)
   integer, intent(in) :: a
   real, intent(inout), dimension(:,:) :: b
   ...
end subroutine foo
#+END_SRC

Local procedures whose names conflict with global ones will likely
confuse the parser.  For example:
#+BEGIN_SRC f90
subroutine foo(a, b)
   ...
end subroutine foo

subroutine bar(a, b)
   ...
   call subroutine foo
   ...
 contains
   subroutine foo
      ...
   end subroutine foo
end subroutine bar
#+END_SRC

Also not handled are overloaded operators, scalar precision modifiers,
like =integer(kind=c_int)=, for which the precision is just ignored, and
many other of the hairier aspects of the fortran language.