Re: Library of Babel confusion

["Berry, Charles" <ccberry@ucsd.edu>]

> On Apr 6, 2018, at 4:59 PM, Thomas S. Dye <tsd@tsdye.com> wrote:
> 

[Tom's response covering the main issues deleted]

> hth,
> Tom
> 
> Lawrence Bottorff writes:
> 
>> I guess I need more information. For example, what is C-c C-v v doing
>> exactly? Then C-x C-e? And  M-x (symbol-function 'myelsquare) doesn't work.


`C-h k' is really your friend here. If you do not know it, try typing it twice `C-h k C-h k'.

As for the specific keystrokes mentioned above:

,----[ C-h k C-c C-v v ]
| C-c C-v v runs the command org-babel-expand-src-block (found in
| org-mode-map), which is an interactive autoloaded compiled Lisp
| function in ‘ob-core.el’.
| 
| It is bound to C-c C-v v, C-c C-v C-v.
| 
| (org-babel-expand-src-block &optional ARG INFO PARAMS)
| 
| Expand the current source code block.
| Expand according to the source code block’s header
| arguments and pop open the results in a preview buffer.
| 
| [back]
`----

In your case, it shows that the `mtelsquare' src block expands to:


,----
| (let ((x (quote 0)))
| (defun myelsquare (x)
|   (* x x))
| )
`----


,----[ C-h k C-x C-e ]
| C-x C-e runs the command eval-last-sexp (found in global-map), which
| is an interactive compiled Lisp function in ‘elisp-mode.el’.
| 
| It is bound to C-x C-e.
| 
| (eval-last-sexp EVAL-LAST-SEXP-ARG-INTERNAL)
| 
| Evaluate sexp before point; print value in the echo area.
| Interactively, with prefix argument, print output into current buffer.
| 
| Normally, this function truncates long output according to the value
| of the variables ‘eval-expression-print-length’ and
| ‘eval-expression-print-level’.  With a prefix argument of zero,
| however, there is no such truncation.  Such a prefix argument
| also causes integers to be printed in several additional formats
| (octal, hexadecimal, and character).
| 
| If ‘eval-expression-debug-on-error’ is non-nil, which is the default,
| this command arranges for all errors to enter the debugger.
| 
| [back]
`----

So with point at the end of the preview buffer for myelsquare (which has one `let' expression it it) it has the same effect as running `eval-buffer'. viz, the elisp function `myelsquare' is created.

If you have gotten this far, there is an lisp function called `myelsquare' and the `symbol-function' expression will return its value when properly `eval'ed. I misspoke before. I should have said 

	M-: (symbol-function 'myelsquare) RET

And that value is `(lambda (x) (* x x))'. Which simply shows you have defun'ed a function and what it is.

Once you have an elisp function, the natural way to call it is src_emacs-lisp{(myelsquare 1.5)}. 

One thing you can do with LOB blocks is use them in header args of src blocks just as you would use calls to ordinary src blocks. 

HTH,

Chuck