Re: [Sbcl-help] help with packages

[Michał H. | K. <mh...@ke...>]

Export N, E, W, S from package TEST1 and use it in TEST2, or otherwise import the symbols. Otherwise you are comparing TEST1::N and TEST::2 for equality; they are not the same symbol, so the set difference will not treat them as equal.

Alternatively, just use keywords: :N, :E, :W, :S will work fine.
________________________________
From: Shadrock Uhuru <niy...@gm...>
Sent: Thursday, June 11, 2026 4:30 PM
To: sbc...@li... <sbc...@li...>
Subject: [Sbcl-help] help with packages

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;; ------------------------------------------------------------------------
CL(1): (defpackage test1
  (:use :cl)
  (:export :test))
#<PACKAGE "TEST1">

CL(2): (in-package :test1)
#<PACKAGE "TEST1">

TEST1(3):

(defun test (test-val)                       ;; remove items from a list
  (format t "~%the test-val = ~a " test-val) ;; items to remove
  (let ((diff-list (set-difference (list 'N 'E 'W 'S) test-val)))  ;; remove the items
    (format t "~%the first item of test-val = ~a "(first  test-val))  ;; just to prove we get the function parameter
                                                                      ;; and we can operate on it
    (format t "~%the diff-list = ~a " diff-list)                     ;; the resultant list
    (dolist (each-item diff-list)                  ;; get each item of resultant list
    (format t "~%each item = ~a" each-item))))     ;; print item

TEST
TEST1(4): (test (list 'N 'S))

the test-val = (N S)
the first item of test-val = N
the diff-list = (W E)
each item = W
each item = E
NIL


TEST1(5): (defpackage test2
  (:use :cl))
#<PACKAGE "TEST2">

TEST1(6): (in-package :test2)
#<PACKAGE "TEST2">

TEST2(7) (test1:test (list 'N 'S))

the test-val = (N S)
the first item of test-val = N
the diff-list = (S W E N)
each item = S
each item = W
each item = E
each item = N
NIL

TEST2(8):

;; ---------------------------------------------
SBCL 2.6.4.openbsd.sbcl-2.6.4

hi everyone
the function above works when i call it within the package it was created in
but when i call it from another package the call to set-difference
appears to get an empty list as its second parameter,
as the test function works when called from it home package,
i'm assuming that the problem lies with how the packages are set up.
can anyone point me to the error in my code.
thanks shadrock


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