Org mode & "literate programming": including files

[Bob Heffernan <bob.heffernan@gmail.com>]

Dear all,

I am new to Emacs (as a long-time vim user) so apologies if this
question has an easy answer, but I've done a bit of searching before
asking.

I am looking at using org-mode for (a fairly simplistic version of)
literate programming.  The programming language I'm using is Scheme,
although this probably doesn't matter.  I've set things up so that
code blocks share a session:

#+PROPERTY: header-args :session *scheme*

and I can then have several code blocks that work nicely together
(these would usually be sprinkled throughout the document, of course,
with text in between):

#+begin_src scheme :results silent                                                                                                                                      (define (f n) (+ n 1))                                                                                                                                              #+end_src
#+begin_src scheme
  (f 1)
#+end_src

If I run the code in each block in turn with C-c C-c, which I guess
calls org-babel-execute-src-block, I get

#+RESULTS:
: 2

So far so good and this is perfect for simple programs.

However, once things get more complicated I will want to include
another such org file, as a library as it were. For example, I'd like
to be able to write a second org file that includes the stuff above
and now knows what the definition of the procedure f is. I know that
there is #+INCLUDE but I guess what I really need is to include a file
and, at the same time, execute all src blocks in that file so that
they are present in the same session as that of my current file.

To give an example, let's say I'm working on writing solutions to
Project Euler problems.  After a while, I'll want a little library of
procedures relating to prime numbers (since these come up a lot) which
I can include as needed.  It would be nice for this to also be written
up nicely in org mode.

I asked this question on the emacs subreddit and the library of babel
was mentioned.  This would work, I guess, but isn't quite what I'm
looking for.  Somebody else mentioned "transclusion" which seems
perhaps more powerful than what I'm looking for.  It seems like this
should be a common problem to solve, but Google hasn't found anything
for me.

Thank you & best regards,
Bob Heffernan