> Sent: Thursday, May 06, 2021 at 4:39 AM > From: "Eric S Fraga" <e.fr...@ucl.ac.uk> > To: "Matt Price" <mopto...@gmail.com> > Cc: pie...@caramail.com, "Org Mode List" <emacs-orgmode@gnu.org> > Subject: Re: Multiple calc commands with orgbabel > > On Wednesday, 5 May 2021 at 11:11, Matt Price wrote: > > Can you explain how you get calc embedded mode working in org? I have > > never used it and it sounds interesting, but I don't understand what > > hte delimiters are. > > Sure. Here is a mini-tutorial! :-) I recently gave an interactive talk > on embedded Calc... > > The out-of-the-box settings for Emacs embedded mode are such that any > line surrounded by empty lines (i.e. couple of blank lines before and > after) can be interpreted as an expression to evaluate by Calc using > "C-x * u". You do not need to place these expressions in any src block. > > The detection can be somewhat fragile so extra blank lines are sometimes > necessary for some reason. > > For instance, copy the following few lines to a text buffer and type > "C-x * u" on each line in turn: > > --8<---------------cut here---------------start------------->8--- > > > x := 180 => > > > y := sin(x / 4) => > > > z := 2 y^2 => > > > --8<---------------cut here---------------end--------------->8--- > > The general format for an embedded calc expression is > > var := expression => value > > where only "expression" is required. If you don't have "=>", evaluating > the expression will replace the expression with its value. > > If you have lines as above, with assignments and values after the actual > expression, you can then go back to the first line and change the value, > say to 90, type "C-x *u" on that line again and all of them should > update. > > The calculations can involve calculus (derivatives, integration), linear > algebra, and units. Calc is actually an incredibly powerful (and > relatively unknown) computer algebra system hiding within Emacs.
Calc is a great piece of work. Has it been long that work was done on it? > The variables that could be customised to have org specific recognition > would be calc-embedded-open-formula and calc-embedded-close-formula. It > might be useful for the community to think about whether org should have > org specific settings for these variables. I actually define settings > for org so that only lines that look like this: > > #+calc: expression > > are interpreted (without requiring empty lines around such lines) > [1]. I then have code for processing these lines on export to LaTeX to > present the equations and results in a more accessible way as I use > embedded calc a lot for teaching (beamer slides). > > Final note: the info manual for embedded Calc mode emphasises editing > the expressions and interacting with Calc while doing so. I find that > method of working rather confusing, tiring, and unproductive (for my use > case) so I write the calc lines using normal editing and only "update" > the expressions to get the results. YMMV, of course. > > Let me know if this helped at all, > eric > > > Footnotes: > [1] it would be nice to have some generic way to hijack C-c C-c on such > lines to do what I want, e.g. calc-embedded-update-formula. > > -- > : Eric S Fraga via Emacs 28.0.50, Org release_9.4.5-395-g82fbdd > >