Notes On org-scraps

org-scraps are interesting because I have only used Org-Mode’s tangling functionality for my Emacs initialization file. They show off a lot of the literate stuff with concise examples. Things make a lot more sense how.

• :sep
• Finally see why this is important: it allows easily handling CSV data. Big deal for working with tables and files. Don’t have to worry about too much fancy stuff when you’ve got Tables, Elisp, and this.
• :results
• pp formats the code as expected, reminding us that this header arg value is for rendering, one of this header arg’s duties
• Uses Emacs-Lisp for Header-Argument: Export results for everything but Beamer.
• output with table collects a new row for every line of output from the shell. Space separates the columns. wc returns one record with 3 columns. Flexible.
• Uses Emacs-Lisp for Header-Argument: Insert results during export but not during evaluation because you want to see it in HTML but not in Org. Good reminder.
• raw seems important.
• org is for document formatting for rich features; that is the difference. How can you wrap raw results? wrap. I had misunderstood this one, it is to obtain Org-Mode formatting, not just handle wrapping.
• :wrap
• Wrap results in a results block by default or whatever type specified. Probably always want to wrap to make results replaceable and removable. Such a big one that I never considered.
• :prologue, :epilogue
• Work as documented. Nice way to evaluate code snippets in a closure so you don’t muck up the global environment. R for example with local.
• :cache
• It works.
• :var
• Set with any value accessible by Emacs-Lisp, including Babel, so, anything.
• Give any Org-Mode named element/entity a name and you get a handle on the entity itself. You can pass that entity in as an argument anywhere. You get it just as it is. If you name an Example-Special block then you can do whatever you want with it. You can use it for argument values. You can use it in literate examples. You have complete access to the entirety of the document to utilize and manipulate as you please. It is easy to configure :results incorrectly here. Like an example block? Bring it’s text anywhere, in the document or a programming language.
• Uses Emacs-Lisp for Header-Argument: You can use lisp for header args. Var is a header arg. You can call anything. Tangle the document before evaluating this block. Maybe do something with the result. Maybe use this as a way to make sure that the tangled files are there before some work is done. Anything is possible. There is a normal control flow.
• Nice VC example with a few variables then used. Revealing of how you can do just about anything.
• :eval
• Uses Emacs-Lisp for Header-Argument: Allow evaluation on export with a check. Example checks and disallows evaluation during export.
• Features
• Tables are first-class entities. Pass as arguments anywhere.
• Call lines
• For Org-Babel evaluation functionality.
• Also to get block-results places.
• In-Line Source-Blocks
• Work fine.
• Remember to consider these more.
• Indexable data: noweb ref data lets you access it by index
• Example given of how to get Org-Macro expansion in tangling!
• Never read sh’s doc; has stdin.
• Thoughts
• Struggling with best way to master Org-Mode Literate Programming. It is flexible and mysterious. Thought that desire to perform a certain task would be best motivator but it isn’t because without understanding the tool itself it wouldn’t ever occur to you to do such things. Perhaps the best approach is to constantly ask yourself how to do what you are doing right now, and then search Org-Scraps.
• While learning Org-Mode I got good at tangling and nothing else.
• With the noweb and call stuff, everything that you would expect possible with any programming language is possible with Babel, between languages, with thoughtful evaluation.
• Everything in Org is text. You can insert links that you generated via any means. Starting to think that the best way to learn Org is to have a need. There are so many possibilities, and I don’t need any of them right now.
• More play is required to learn Org-Babel.
• “large code in inline blocks” example shows how you might insert text programmatically instead of using macros. Everyone has wondered if that is a better way to do it.
• Org-Mode Table into SQL is nice.
• Can’t have two VAR’s in a properties block but have alternatives
• List of values
• Table of name value pairs
• Don’t just go naming things in other people’s Webs
• “noweb then variables” example shows how to reuse code-snippets.
• “new file handling” example worth doing to test your config
• Nice Graphviz example
• LoB has the code to read and write tables to file
• Pattern #+TBLFM: $2='(sbe leftover (prefix$\$1)).
• Named result blocks can appear anywhere.

Code

Should work in order.

  (format "%S%S%S" a b c)

| 000 |


noweb referernces

• What is going on here?
  a = 28

  # <<noweb-example>>
a + 4

32