2015-02-06

Emacs Org Mode Bable bug. For emacs lisp, session is always on

Emacs Org Mode Bable bug. For emacs lisp, session is always on.

* test session; no session

#+BEGIN_SRC emacs-lisp :exports both
(setq x 3)
#+END_SRC

#+RESULTS:
: 3

#+BEGIN_SRC emacs-lisp :exports both
(+ 2 x)
#+END_SRC

#+RESULTS:
: 5

save the above as session-test.org, then open it, M-x org-mode. Move cursor to the elisp code block, press C-c C-c to eval. Repeat for the second block.

The expected result for second block should be error of unknown variable x.

2015-02-02

emacs: xah fly keys, harmless key maps

Global Bindings Starting With <menu> n:
key             binding
---             -------

<menu> n RET    Prefix Command
<menu> n SPC    Prefix Command
<menu> n 0      shell-command-on-region
<menu> n 1      set-input-method
<menu> n 2      global-hl-line-mode
<menu> n 3      whitespace-mode
<menu> n 4      linum-mode
<menu> n 5      visual-line-mode
<menu> n 6      calendar
<menu> n 7      calc
<menu> n 8      shell
<menu> n 9      shell-command
<menu> n a      text-scale-adjust
<menu> n b      toggle-debug-on-error
<menu> n c      toggle-case-fold-search
<menu> n d      narrow-to-page
<menu> n e      eshell
<menu> n f      Prefix Command
<menu> n g      toggle-frame-fullscreen
<menu> n h      widen
<menu> n i      make-frame-command
<menu> n n      narrow-to-region
<menu> n r      read-only-mode
<menu> n s      flyspell-buffer
<menu> n t      narrow-to-defun
<menu> n u      menu-bar-open
<menu> n w      eww

<menu> n SPC h  xah-toggle-read-novel-mode
<menu> n SPC n  xah-toggle-line-spacing
<menu> n SPC t  xah-toggle-margin-right

<menu> n f C-f  find-file-other-frame
<menu> n f C-o  display-buffer-other-frame
<menu> n f .    find-tag-other-frame
<menu> n f 0    delete-frame
<menu> n f 1    delete-other-frames
<menu> n f 2    make-frame-command
<menu> n f b    switch-to-buffer-other-frame
<menu> n f d    dired-other-frame
<menu> n f f    find-file-other-frame
<menu> n f m    compose-mail-other-frame
<menu> n f o    other-frame
<menu> n f r    find-file-read-only-other-frame

<menu> n RET F  set-file-name-coding-system
<menu> n RET X  set-next-selection-coding-system
<menu> n RET c  universal-coding-system-argument
<menu> n RET f  set-buffer-file-coding-system
<menu> n RET k  set-keyboard-coding-system
<menu> n RET l  set-language-environment
<menu> n RET p  set-buffer-process-coding-system
<menu> n RET r  revert-buffer-with-coding-system
<menu> n RET t  set-terminal-coding-system
<menu> n RET x  set-selection-coding-system

These are keys starting with 【▤ Menu n】 from xah fly keys Mode. This key set is for commands that are “harmless” — even if called accidentally. They usually do prompt or do some display changes, and never edit anything.

What's the Impetus that Made Lambda Calculus So Powerful?

what's lambda calculus? It's a notation, and nothing but syntax & notation.

The λ-calculus is, at heart, a simple notation for functions and application. The main ideas are applying a function to an argument and forming functions by abstraction. The syntax of basic λ-calculus is quite sparse, making it an elegant, focused notation for representing functions. Functions and arguments are on a par with one another. The result is an intensional theory of functions as rules of computation, contrasting with an extensional theory of functions as sets of ordered pairs. Despite its sparse syntax, the expressiveness and flexibility of the λ-calculus make it a cornucopia of logic and mathematics. This entry develops some of the central highlights of the field and prepares the reader for further study of the subject and its applications in philosophy, linguistics, computer science, and logic.

http://plato.stanford.edu/entries/lambda-calculus/

and that's why, syntax is the most important thing in languages. Programing Language Syntax Soup