Common lisp load package from name in string

Question

I'm using mod_lisp along with the modlisp-clisp.lisp file at http://www.fractalconcept.com/fcweb/download/modlisp-clisp.lisp. I want to load different packages based on the server-id field so I can have different sites set up. I was trying to do this with

(server-id:fetch-content request)

with server-id quoted and unquoted, but it couldn't find the package. Some document-hunting found me find-package, but when I do

((find-package server-id):fetch-content request)

it says

(FIND-PACKAGE SERVER-ID) should be a lambda expression.

How can I load a package given the package name as a string?

Rainer Joswig · Accepted Answer · 2014-05-19 21:37:46Z

1

If you want to use different symbols when calling functions, you have to compute them.

(funcall (find-symbol (compute-the-name) (compute-the-package))
         arg1 ... argn)

Note that both package and symbol names are usually uppercase strings.

CL-USER 6 > (funcall (find-symbol "EXPT" "CL") 3 4)
81

Note that you should not let the user over the network specify arbitrary functions and arguments which are then called without error checking.

answered May 19, 2014 at 21:37

Rainer Joswig

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sds · Accepted Answer · 2014-05-19 20:55:06Z

0

Common Lisp packages are what other systems call namespaces.

You have to use load or require - or whatever the documentation instructs you to do - to make the desired functionality (including the packages and functions) available.

Once the code is loaded into Lisp, you can use list-all-packages to see which packages are now available.

edited May 19, 2014 at 20:55

answered May 19, 2014 at 20:41

sds

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2 Comments

user3654025 Over a year ago

I know, I'm doing that. The file is getting loaded but if I call a function defined in that file it's not recognized. So I was trying to prefix the package name onto the function but don't know how to get from the string to something I can use as a package name.

sds Over a year ago

are you running in modern mode (non-case-converting)?

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