[racket] Evaluating Racket source files from within another Racket source file

From: Matthew Butterick (mb.list.acct at gmail.com)
Date: Sat Apr 27 21:16:00 EDT 2013

Aha, combining enter! with dynamic-require seems to do the trick:

(define (route req)
    (enter! "module.rkt")
    (define foo (dynamic-require "module.rkt" 'foo))
    (response/xexpr `(p ,(format "~a" foo))))

Once this route is running in the web server, I can make changes to
module.rkt, then click reload in the browser, and the changes will appear
in the browser.

If this is a terrible idea let me know, otherwise I'll consider this

On Sat, Apr 27, 2013 at 9:56 AM, Matthew Butterick
<mb.list.acct at gmail.com>wrote:

> I'm building a website using Scribble as the source format. As a
> development tool, I've built a web server in Python that lets me view all
> my Scribble source files and look at them in different states of
> processing. To view the results of the Scribble files, the Python server
> just sends the files to Racket via a system command (os.Popen) and reads
> the result. This works but it's slow, because it  has to launch a new
> Racket thread for every request.
> I thought I could speed things up by rewriting the development web server
> in Racket. But having tried a few approaches, I'm not sure how to duplicate
> this functionality within a Racket web servlet:
> *(require <modulename>) *
> This only gets evaluated once, when the server is started. That doesn't
> help, since the <filename> is going to be passed in as a parameter while
> the server is running.
> *(dynamic-require <** modulename **>) *
> This gets evaluated only when invoked, and thus can take <modulename> as a
> parameter, but then <filename> can't be reloaded (this is essential, as the
> point of the system is to be able to edit the files and see the changes in
> the web browser immediately)
> *(enter! <modulename>)*
> This reloads the file, but it's not clear how to get access to names
> provided by <modulename>. (The documentation for enter! suggests that this
> is not how it's meant to be used anyhow.)
> Obviously, I could call a new instance of Racket as a system command, but
> that wouldn't offer any advantage over the current approach.
> I suppose what I'm looking for is an equivalent of the Python
> reload(<modulename>) command.
> Matthew Butterick
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