Add episode 8 to the videos.org

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@@ -415,7 +415,8 @@ CLOSED: [2022-06-13 Mon 10:38]
 - https://www.gnu.org/software/emacs/manual/html_node/elisp/Plist-Access.html
 - https://www.gnu.org/software/emacs/manual/html_node/elisp/Plists-and-Alists.html
 
-* Episode 7 - Basic Loops
+* DONE Episode 7 - Basic Loops
+CLOSED: [2022-07-09 Sat 10:31]
 ** About previous episode
 - Duplicate keys in an association list
 - ~eval-defun~
@@ -488,4 +489,70 @@ CLOSED: [2022-06-13 Mon 10:38]
 
 * Episode 8 - More Loops
 ** Recursion
+- A *Recursive* function, is a function that defines in terms of itself
+- Easy to implement
+- But should be careful with it to aviod infinit loops
+
+*** Example
+#+BEGIN_SRC emacs-lisp
+  (defun foo (int)
+    (print int)
+    (when  (> int 0)
+      (foo (- int 1))))
+
+  (foo 10)
+#+END_SRC
+
 ** Functional style loops
+*** Mapping functions Family
+- ~mapcar~
+#+BEGIN_SRC emacs-lisp
+  (mapcar #'1+ '(1 2 3 4 5))
+
+  (mapcar (lambda (x) (* x x))
+          '(1 2 3 4))
+#+END_SRC
+
+- ~mapc~
+#+BEGIN_SRC emacs-lisp
+  (mapc #'1+ '(1 2 3 4 5))
+  (mapc #'print '(1 2 3 4 5))
+#+END_SRC
+
+- ~map-concat~
+#+BEGIN_SRC emacs-lisp
+  (mapconcat (lambda (x)
+               (format "[%s]" x))
+             '(1 2 3 4 5)
+             " <|> ")
+#+END_SRC
+
+*** Seq module
+A collection of handy functions that operate on ~sequences~.
+
+- ~seq-reduce~
+#+BEGIN_SRC emacs-lisp
+  (require 'seq)
+
+  (seq-reduce
+
+   (lambda (acc x)
+     (+ acc x))
+
+   '(1 2 3 4)
+
+   0)
+#+END_SRC
+
+- ~seq-filter~
+#+BEGIN_SRC emacs-lisp
+  (seq-filter (lambda (x) (< x 10))
+              '(8 12 22 9))
+#+END_SRC
+- ~seq-partition~
+#+BEGIN_SRC emacs-lisp
+  (seq-partition '(a b c d e f) 2)
+
+#+END_SRC
+- ~seq-min~, ~seq-max~
+* Episode 9 - Basics of Macros