add join function to stdlib

Signed-off-by: Ava Affine <ava@sunnypup.io>

snippets/avas-laptop-prompt.f

@@ -16,7 +16,7 @@
 ;; You should have received a copy of the GNU General Public License
 ;; along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
-;; AVA'S LAPTOP PROMPT
+;; AVAS LAPTOP PROMPT
 ;; This file contains a shell prompt configuration that outputs current dir
 ;; username, and percentages for all batteries on the system.
 ;; -> requires CFG_FLESH_POSIX=true and userlib.

snippets/userlib-tests.f

@@ -114,6 +114,12 @@
          (add-path new-path)
          (contains? (get-paths) new-path))))
 
+    ('join operates as expected'
+      (quote
+        (let ((l ("1" 2 (3))))
+          (eq? (join l ".")
+               "1.2.(3)"))))
+
      ;; add more test cases here
    ))
 

snippets/userlib.f

@@ -146,3 +146,13 @@ adds a directory to PATH'
             (rem (cdr path-iter)))
         (echo pat)
         (set (q path-iter) (pop rem))))))
+
+(def join
+'concatenates list elements into a string, while
+interspersing a provided delimiter in between elements'
+  (list delim)
+  (reduce (lambda (res elem)
+            (if (eq? (strlen res) 0)
+              (string elem) 
+              (concat res delim elem)))
+    list))