Finish up episode 12

docs/videos.org

@@ -1,4 +1,4 @@
-#+TITLE: How to build an editor with Emacs Lisp
+#+TITLE: Emacs From Scratch - An Emacs tutorial for beginners
 #+SEQ_TODO: TODO(t/!) NEXT(n/!) BLOCKED(b@/!) | DONE(d%) CANCELLED(c@/!) FAILED(f@/!)
 #+TAGS: READER(r) MISC(m)
 #+STARTUP: logdrawer logdone logreschedule indent content align constSI entitiespretty overview
@@ -628,7 +628,8 @@ CLOSED: [2022-11-04 Fri 15:25]
 ** Real Examples
 Let's discuss ~defflag~ and ~when-flag~ macros in [[file:../core/fg42/flags.el]]
 
-* Episode 11 - Common pitfalls of Macros
+* DONE Episode 11 - Common pitfalls of Macros
+CLOSED: [2022-12-04 Sun 12:15]
 ** Compiletime vs runtime
 #+BEGIN_SRC emacs-lisp
   ;; `do-something-with-side-effect' evaluates on compile time
@@ -704,3 +705,75 @@ Never evaluate the arguments of a macro manually. E.g. with =eval=
 
 More info: https://www.gnu.org/software/emacs/manual/html_node/elisp/Eval-During-Expansion.html
 ** What's next?
+* Episode 12 - Features & Load Paths
+** Emacs Lisp files
+Write elisp code in files with =.el= suffix.
+
+*** Batch mode
+Execute an elisp file via Emacs in a non-interactive (script like) fashion:
+
+#+BEGIN_SRC bash
+emacs --batch -l /path/to/the/file
+#+END_SRC
+
+*** =load= function
+Loads an elisp file into the running Emacs process. For more info ~C-h f load~.
+#+BEGIN_SRC emacs-lisp
+  (load "/path/to/the/file")
+  (load "PATH1")
+#+END_SRC
+
+- It first looks for the =PATH + .elc= combination
+- If not successful, looks for the =PATH + .el= combination
+- If not successful, looks for platform dependent suffixes
+- If not successful, tries to load the =PATH= as it is
+
+** Load Path
+*** =load-path=
+List of directories to search for files to load.
+
+#+BEGIN_SRC emacs-lisp
+  (add-to-list 'load-path "/path/to/a/directory")
+#+END_SRC
+
+*** =EMACSLOADPATH= environment variable
+
+** Emacs =feature=
+Emacs tracks loaded packages and file via =features=. Each elisp file can =provide=, zero or
+more =features=.
+
+Features are just symbols.
+
+*** =features= list
+A list of all loaded features. For more info, try ~C-h v features~.
+
+*** =featurep=
+A predicate function to check whether a feature is loaded or not.
+
+#+BEGIN_SRC emacs-lisp
+  (featurep 'some-feature)
+#+END_SRC
+
+*** =provide=
+
+#+BEGIN_SRC emacs-lisp
+  (provide 'some-feature)
+#+END_SRC
+
+*** =require=
+If the given feature as the parameter is not loaded yet, loads it via the =load=
+function. For more info, ~C-h f require~.
+
+#+BEGIN_SRC emacs-lisp
+  (require 'some-feature)
+
+  ;; Or
+
+  (require 'some-feature "/path/to/file")
+#+END_SRC
+
+** Installing Emacs packages the hard way
+We can clone a library somewhere on the disk and add the path to it to the =load-path= list
+and load the library files.
+
+But that would be tedious to do so for all the libraries. That's why we use a package manager