How to require a file whose path depends on a get-env value?

[Kathi Fisler]

We need to be able to construct a path to require based on a command-line argument.  We currently put the command-line value into an environment variable, using get-env to extract the value. In other words, we want to do (the equivalent of)

     (require (string-append "courses" (get-env WHICHCLASS) "defs.rkt"))

How can we pull off something with this behavior, since evaluating seems incompatible with require syntax.

thanks,

Kathi

[Jay McCarthy]

You can use dynamic-require and grab the identifiers you need one by
one. Fine if there are few.

You can set up a namespace, dynamic-require into it, and then eval the
code you want inside the namespace. Okay for many ids, but code to run
will be a little painful to write, so hopefully small.

You can make a macro expand to the require and look at get-env in the
compile-time, but now you have to compile and run your code rather
than compiling it first. My guess is that this is not a big deal for
your use case. I'd recommend this if you can.

Jay

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--
-=[ Jay McCarthy http://jeapostrophe.github.io ]=-
-=[ Associate Professor PLT @ CS @ UMass Lowell ]=-
-=[ Moses 1:33: And worlds without number have I created; ]=-