Finish up ep number 9

docs/videos.org

@@ -487,7 +487,8 @@ CLOSED: [2022-07-09 Sat 10:31]
         (message ">> %s" x))))
 #+END_SRC
 
-* Episode 8 - More Loops
+* DONE Episode 8 - More Loops
+CLOSED: [2022-07-29 Fri 15:11]
 ** Recursion
 - A *Recursive* function, is a function that defines in terms of itself
 - Easy to implement
@@ -555,4 +556,49 @@ A collection of handy functions that operate on ~sequences~.
 
 #+END_SRC
 - ~seq-min~, ~seq-max~
-* Episode 9 - Basics of Macros
+* Episode 9 - Introduction to Macros
+** What is a macro?
+- A macro is defined much like a function
+- It works on compile time
+- It returns a new expression as the return value
+- The compiler "expands" a macro by replacing the macro call with the return value of the macro
+- Different evaluation rule than functions
+  + Unlike function calls, the arguments to a macro will be passed to the macro as they are,
+    without evaluation.
+- Macros vs inline functions
+
+** How to define and expand a macro?
+- We can define a macro using ~defmacro~ form
+
+#+BEGIN_SRC emacs-lisp
+  (defmacro inc (val)
+    (list #'1+ val))
+
+  (defmacro mydef (name val)
+    (list 'setq (intern (concat "my-" (symbol-name name))) val))
+
+  (defmacro foo (val)
+      (1+ val))
+#+END_SRC
+
+- We can inspect the expansion process using the ~macroexpand~ function family.
+  + ~macroexpand~: Expands the macros until no macro exists in the top level forms
+  + ~macroexpand-all~: Expands the macros all the way down to the subforms
+  + ~macroexpand-1~: Expands the macro only for one level or cycle
+
+#+BEGIN_SRC emacs-lisp
+  (macroexpand-1 '(inc 10))
+  (macroexpand-1 '(mydef blah 20))
+  (print (macroexpand-1 '(when (> 10 5) (print "something"))))
+
+#+END_SRC
+
+** Feedback or question
+- https://lxsameer.com
+- [[https://twitter.com/lxsameer][@lxsameer]] on Twitter
+
+* Episode 10 - More on Macros
+** Quasiquotes aka back quote
+** ~declare~ form
+* Episode 11 - Common pitfalls of Macros
+*