Introduce `tempo' subsections and reduce line count in source blocks

README.org

@@ -152,6 +152,9 @@ Here follows a list of links on how to use Emacs and Elisp:
    the best approach to learn Emacs and Elisp.
 5. [[https://www.masteringemacs.org/][Mastering Emacs]] is a link to a blog with many interesting posts that promotes
    a book on how to become a proficient Emacs user.
+6. [[https://www2.lib.uchicago.edu/keith/emacs/][Use GNU Emacs: The Plain Text Computing Environment]] explains the fundamentals
+   of the Emacs abstractions before showing how to exploit those abstractions
+   interactively.  It targets a similar audience as the [[https://www.masteringemacs.org/][Mastering Emacs]] book.
 
 * [[info:emacs#Early Init File][Early Init File (info)]]
 :PROPERTIES:
@@ -2054,6 +2057,7 @@ list detailing and motivating each listing:
      (gnuplot . ,(fboundp 'gnuplot-mode))
      (js . t)
      (latex . t)
+     (lilypond . ,(fboundp 'lilypond-mode))
      (lisp . t)
      (lua . ,(fboundp 'lua-mode))
      (maxima . ,(fboundp 'maxima-mode))
@@ -2074,18 +2078,7 @@ list detailing and motivating each listing:
                  ol-info
                  org-id
                  org-protocol
-                 org-tempo)
-   org-structure-template-alist '(("a" . "export ascii")
-                                  ("c" . "center")
-                                  ("C" . "comment")
-                                  ("e" . "example")
-                                  ("E" . "export")
-                                  ("h" . "export html")
-                                  ("l" . "export latex")
-                                  ("q" . "quote")
-                                  ("s" . "src")
-                                  ("p" . "src python -n -i :session")
-                                  ("v" . "verse"))))
+                 org-tempo)))
 #+end_src
 
 #+caption[Setup =org-babel=]:
@@ -2417,7 +2410,7 @@ else:
 #+caption: Find valid entries for  =org-babel-load-languages=.
 #+name: lst:valid-org-babel-load-languages-entries
 #+header: :wrap "src emacs-lisp :results silent :tangle no"
-#+begin_src emacs-lisp :exports both :results value pp :exports both
+#+begin_src emacs-lisp :exports both :results value pp
 (defun all-org-babel-execute-fns ()
   "Find `ob-LANGUAGE' files in Org defining `org-babel-execute:LANGUAGE'.
 
@@ -4532,6 +4525,96 @@ src_emacs-lisp{(describe-function 'inferior-emacs-lisp-mode)}.
   (setopt ielm-dynamic-return nil))
 #+end_src
 
+*** [[https://emacs.stackexchange.com/questions/2129/why-is-let-faster-with-lexical-scope][Disassemble dynamical and lexical scope]]
+:PROPERTIES:
+:CUSTOM_ID: sec:disassemble-dynamical-lexical-scope
+:header-args:emacs-lisp: :exports code :tangle no
+:END:
+
+Listing [[lst:disassemble-lexical-scope][lexical scope disassembly]] and [[lst:disassemble-dynamical-scope][dynamical scope disassembly]] disassemble
+identical code in case of respectively lexical and dynamical scope. Listing
+[[lst:disassemble-lexical-scope-results][lexical scope disassembly results]] and [[lst:disassemble-dynamical-scope-results][dynamical scope disassembly results]] show
+the respective results.
+
+The link [[https://emacs.stackexchange.com/questions/61754/how-can-i-enable-lexical-binding-for-elisp-code-in-org-mode][how to enable lexical scope for Emacs Lisp in org-mode source blocks]]
+explains all possibilities of disabling or enabling lexical scope.
+
+#+caption[Disassemble lexical scope]:
+#+caption: Disassemble lexical scope.
+#+name: lst:disassemble-lexical-scope
+#+header: :wrap "src text -n"
+#+begin_src emacs-lisp -n :exports both :lexical t :results value
+(with-temp-buffer
+  (disassemble (lambda (n)
+                 "Demonstrate lexical scope."
+                 (let* ((lower most-negative-fixnum)
+                        (upper most-positive-fixnum)
+                        (sum (+ lower upper)))
+                   (expt sum n)))
+               (current-buffer))
+  (buffer-substring-no-properties (point-min) (point-max)))
+#+end_src
+
+#+caption[Disassemble lexical scope results]:
+#+caption: Disassemble lexical scope results.
+#+name: lst:disassemble-lexical-scope-results
+#+RESULTS: lst:disassemble-lexical-scope
+#+begin_src text -n
+byte code:
+  doc:  Demonstrate lexical scope. ...
+  args: (arg1)
+0       varref    most-negative-fixnum
+1       varref    most-positive-fixnum
+2       stack-ref 1
+3       stack-ref 1
+4       plus
+5       constant  expt
+6       stack-ref 1
+7       stack-ref 5
+8       call      2
+9       return
+#+end_src
+
+#+caption[Disassemble dynamical scope]:
+#+caption: Disassemble dynamical scope.
+#+name: lst:disassemble-dynamical-scope
+#+header: :wrap "src text -n"
+#+begin_src emacs-lisp -n :exports both :results value
+(with-temp-buffer
+  (disassemble (lambda (n)
+                 "Demonstrate lexical scope."
+                 (let* ((lower most-negative-fixnum)
+                        (upper most-positive-fixnum)
+                        (sum (+ lower upper)))
+                   (expt sum n)))
+               (current-buffer))
+  (buffer-substring-no-properties (point-min) (point-max)))
+#+end_src
+
+#+caption[Disassemble dynamical scope results]:
+#+caption: Disassemble dynamical scope results.
+#+name: lst:disassemble-dynamical-scope-results
+#+RESULTS: lst:disassemble-dynamical-scope
+#+begin_src text -n
+byte code:
+  doc:  Demonstrate lexical scope.
+  args: (n)
+0       varref    most-negative-fixnum
+1       varbind   lower
+2       varref    most-positive-fixnum
+3       varbind   upper
+4       varref    lower
+5       varref    upper
+6       plus
+7       varbind   sum
+8       constant  expt
+9       varref    sum
+10      varref    n
+11      call      2
+12      unbind    3
+13      return
+#+end_src
+
 ** [[https://fennel-lang.org/][Fennel Programming]]
 :PROPERTIES:
 :CUSTOM_ID: sec:fennel-programming
@@ -4977,9 +5060,14 @@ ruff "$@" | cat
 :header-args: :eval never-export
 :END:
 
+Listing [[lst:shell-pip-list-outdated]] and [[lst:shell-pip-index-versions]] are two
+examples of invoking [[https://pip.pypa.io/en/stable/][pip]] in =org-mode= =shell= source blocks with the respective
+results in listing [[lst:shell-pip-list-outdated-results]] and
+[[lst:shell-pip-index-versions-results]].
+
 #+caption[Show how to use =pip list --outdated=]:
 #+caption: Show how to use =pip list --outdated=.
-#+header: :wrap src text
+#+header: :wrap "src text -n"
 #+name: lst:shell-pip-list-outdated
 #+begin_src shell :exports both :results verbatim
 # WARNING: "pip index" is currently an experimental command.
@@ -4988,12 +5076,13 @@ pip list --outdated
 
 #+caption[The result of =pip list --outdated=]:
 #+caption: The result of =pip list --outdated=.
+#+name: lst:shell-pip-list-outdated-results
 #+RESULTS: lst:shell-pip-list-outdated
-#+begin_src text
+#+begin_src text -n
 Package             Version Latest Type
 ------------------- ------- ------ -----
 aiofiles            22.1.0  23.1.0 wheel
-jupyter_server_ydoc 0.6.1   0.7.0  wheel
+jupyter_server_ydoc 0.6.1   0.8.0  wheel
 jupyter-ydoc        0.2.2   0.3.4  wheel
 y-py                0.5.9   0.6.0  wheel
 ypy-websocket       0.8.2   0.8.4  wheel
@@ -5001,7 +5090,7 @@ ypy-websocket       0.8.2   0.8.4  wheel
 
 #+caption[Show how to use =pip index versions=]:
 #+caption: Show how to use =pip index versions=.
-#+header: :wrap src text
+#+header: :wrap "src text -n"
 #+name: lst:shell-pip-index-versions
 #+begin_src shell :exports both :results verbatim
 # WARNING: "pip index" is currently an experimental command.
@@ -5010,8 +5099,9 @@ pip index versions circular-buffer --no-color
 
 #+caption[The result of =pip index versions=]:
 #+caption: The result of =pip index versions=.
+#+name: lst:shell-pip-index-versions-results
 #+RESULTS: lst:shell-pip-index-versions
-#+begin_src text
+#+begin_src text -n
 circular-buffer (0.2.0)
 Available versions: 0.2.0, 0.1.1, 0.1.0
 #+end_src
@@ -5037,6 +5127,7 @@ Available versions: 0.2.0, 0.1.1, 0.1.0
                   (string-replace "_" "-" (alist-get 'name (car alists))))
           (setq alists (cdr alists))))
       (kill-buffer)
+      (describe-variable 'pip-outdated-packages)
       (message "Calling `%S' succeeded" #'pip-list-outdated))))
 
 (defun pip-list-outdated ()
@@ -5057,14 +5148,22 @@ This invokes an asynchonous process and finishes with a message."
 #+caption: Emacs interface to upgrade outdated unfrozen Python packages.
 #+name: lst:pip-upgrade-maybe
 #+begin_src emacs-lisp -n :results silent
-(defcustom pip-frozen-packages '("aiofiles"
-                                 "jupyter-server-ydoc"
-                                 "jupyter-ydoc"
-                                 "y-py"
-                                 "ypy-websocket")
-  "Frozen Python packages (until jupyterlab-4.0.0)"
+(defgroup pip nil
+  "Client for accessing the \"Package Installer for Python\" and \"PyPI\"."
+  :group 'applications)
+
+(defcustom pip-frozen-packages nil
+  "Frozen Python packages."
+  :group 'pip
   :type '(repeat string))
 
+;; Frozen until the release of jupyterlab-4.0.0.
+(setopt pip-frozen-packages '("aiofiles"
+                              "jupyter-server-ydoc"
+                              "jupyter-ydoc"
+                              "y-py"
+                              "ypy-websocket"))
+
 (defun pip--upgrade-maybe-sentinel (process event)
   (when (and (eq (process-status process) 'exit)
              (buffer-live-p (process-buffer process)))
@@ -5096,16 +5195,72 @@ buffer to check whether upgrading has made the dependencies incompatible."
 
 #+caption[Emacs interface to the =PyPI= simple =JSON= =API=]:
 #+caption: Emacs interface to the =PyPI= simple =JSON= =API=.
-#+name: lst:pip-pypi-simple-json-apip
-#+begin_src emacs-lisp -n :results silent
-(defun pip-simple-json-project-details (name)
-  (let ((url (format "https://pypi.org/simple/%s" name))
-        (url-request-method "GET")
-        (url-mime-accept-string "application/vnd.pypi.simple.latest+json"))
-    (url-retrieve url
-                  (lambda (status) (switch-to-buffer (current-buffer))))))
+#+name: lst:pip-pypi-simple-json-api
+#+begin_src emacs-lisp -n :lexical t :results silent
+;; https://emacs.stackexchange.com/questions/61754/
+;; "How can I enable lexical binding for elisp code in Org mode?"
 
-(defun pip-simple-json-project-list ()
+(defvar pip--simple-details-cache (make-hash-table :test 'equal)
+  "Cache for PyPI project details")
+
+(defun pip-simple-get-json ()
+  (save-excursion
+    (goto-char (point-min))
+    (and (re-search-forward "^HTTP/.+ 200 OK$" nil (line-end-position))
+         (search-forward "\n\n" nil t)
+         (json-parse-buffer :array-type 'list))))
+
+(defun pip-simple-details-retrieve (name callback &optional cbargs)
+  (pip--simple-details-prune-cache)
+  (if-let ((cached (gethash name pip--simple-details-cache)))
+      (apply callback (cdr cached) cbargs)
+    (let ((url (format "https://pypi.org/simple/%s" name))
+          (url-request-method "GET")
+          (url-mime-accept-string "application/vnd.pypi.simple.latest+json"))
+      (url-retrieve
+       url
+       (lambda (status)
+         (let ((details (and (not (plist-get status :error))
+                             (pip-simple-get-json))))
+           (when details
+             (setf (gethash name pip--simple-details-cache)
+                   (cons (time-convert nil 'integer) details)))
+           (prog1
+               (apply callback (or details 'error) cbargs)
+             (kill-buffer))))
+       nil t))))
+
+(defun pip--simple-details-prune-cache ()
+  (let ((expired nil)
+        (time (- (time-convert nil 'integer)
+                 ;; Ten minutes
+                 (* 10 60))))
+    (maphash (lambda (key val)
+               (when (< (car val) time)
+                 (push key expired)))
+             pip--simple-details-cache)
+    (dolist (key expired)
+      (remhash key pip--simple-details-cache))))
+#+end_src
+
+#+caption[Using the Emacs interface to the =PyPI= simple =JSON= =API=]:
+#+caption: Using the Emacs interface to the =PyPI= simple =JSON= =API=.
+#+name: lst:using-pip-pypi-simple-json-api
+#+begin_src emacs-lisp -n :lexical t :results silent
+;; https://emacs.stackexchange.com/questions/61754/
+;; "How can I enable lexical binding for elisp code in Org mode?"
+
+(defun pip-simple-project-versions (name)
+  "Return the versions of Python package NAME."
+  (interactive "sPython package name: ")
+  (pip-simple-details-retrieve
+   name
+   (lambda (details)
+     (when-let ((versions (reverse (cdr (gethash "versions" details)))))
+       (message "`%s' versions: %S" name versions)))))
+
+(defun pip-simple-project-list ()
+  "Get the Python package project list (PEP-691 and PEP-700)."
   (interactive)
   (let ((url-request-method "GET")
         (url-mime-accept-string "application/vnd.pypi.simple.latest+json"))
@@ -5501,9 +5656,9 @@ contrary to for instance [[https://github.com/Fanael/rainbow-delimiters#readme][
 :CUSTOM_ID: sec:electric-operators
 :END:
 
-Listing [[lst:configure-electric-operator]] configures =electric-operator-mode=
-to add spaces around operators for compatibility with for instance the [[https://black.readthedocs.io/en/stable/][Black
-code formatter for Python]].
+Listing [[lst:configure-electric-operator]] configures =electric-operator-mode= to
+add spaces around operators for compatibility with for instance the [[https://black.readthedocs.io/en/stable/][Black code
+formatter for Python]].
 
 #+caption[Configure =electric-operator=]:
 #+caption: Configure =electric-operator=.
@@ -5555,7 +5710,7 @@ Listing [[lst:configure-tempo-latex-completing-read]] shows how to combine =temp
 #+caption: Configure =tempo= user-interface.
 #+name: lst:configure-tempo-ui
 #+begin_src emacs-lisp -n :results silent
-(with-eval-after-load 'tempo
+(when (require 'tempo nil 'noerror)
   (setopt tempo-interactive t)
 
   (with-eval-after-load 'marginalia
@@ -5589,31 +5744,30 @@ Allows `tempo' expansion by typing <SPC> after a complete `tempo' tag."
       (unless (abbrev-symbol (car tag) abbrev-table)
         (define-abbrev abbrev-table
           (car tag) 1 'abbrev-tempo-expand-if-complete)))))
-
-(with-eval-after-load 'org
-  (add-hook 'org-mode-hook 'setup-local-tempo-key-bindings))
 #+end_src
 
+*** Tempo for =AUCTeX='s =LaTeX-mode=
+:PROPERTIES:
+:CUSTOM_ID: sec:tempo-latex
+:END:
+
 #+caption[Configure =tempo= for =latex= with =completing-read=]:
 #+caption: Configure =tempo= for =latex= with =completing-read=.
 #+name: lst:configure-tempo-latex-completing-read
 #+begin_src emacs-lisp -n :results silent
 (with-eval-after-load 'latex
-  (unless (featurep 'tempo)
-    (require 'tempo))
+  (require 'tempo nil 'noerror)
 
   (defun tempo-latex-environment-handler (element)
-    (when-let ((ok (eq element 'latex-environment))
-               (environment
-                (completing-read "LaTeX environment: "
-                                 (LaTeX-environment-list)
-                                 #'always 'require-match)))
-      `(l "\\begin{" ,environment "}" > n > r n "\\end{" ,environment "}" >)))
+    (when (eq element 'latex-environment)
+      (let ((environment (completing-read "LaTeX environment: "
+                                          (LaTeX-environment-list)
+                                          #'always 'require-match)))
+        `(l "\\begin{" ,environment "}" > n > r n "\\end{" ,environment "}" >))))
 
   (cl-pushnew 'tempo-latex-environment-handler tempo-user-elements)
 
   (defun setup-tempo-latex ()
-    (setup-local-tempo-key-bindings)
     (defvar latex-tempo-tags nil)
 
     (tempo-define-template
@@ -5624,18 +5778,24 @@ Allows `tempo' expansion by typing <SPC> after a complete `tempo' tag."
      'latex-tempo-tags)
 
     (tempo-use-tag-list 'latex-tempo-tags)
-    (add-tempo-tags-to-abbrev-table latex-tempo-tags latex-mode-abbrev-table))
+    (add-tempo-tags-to-abbrev-table latex-tempo-tags latex-mode-abbrev-table)
+    (setup-local-tempo-key-bindings))
 
   (add-hook 'LaTeX-mode-hook 'setup-tempo-latex))
 #+end_src
 
+
+*** Tempo for =python-mode=
+:PROPERTIES:
+:CUSTOM_ID: sec:tempo-python
+:END:
+
 #+caption[Configure =tempo= for =python-mode=]:
 #+caption: Configure =tempo= for =python-mode=.
 #+name: lst:setup-python-tempo
 #+begin_src emacs-lisp -n :results silent
 (with-eval-after-load 'python
-  (unless (featurep 'tempo)
-    (require 'tempo))
+  (require 'tempo nil 'noerror)
 
   (defun setup-tempo-python ()
     (defvar python-tempo-tags nil)