Org Flashcards

Spaced-repetition system for use with Emacs org-mode.

Org-fc has been tested with org-mode version 9.3.6 and gawk version 5.1.0. You can check your versions with M-x org-version and gawk -V.

Introduction

In the most abstract sense, this package deals with

Attaching timestamped review information to headlines
Querying all headings where reviews are due
Reviewing due positions of headings

As mentioned in step 3, a heading can have multiple positions, e.g. to implement cloze-deletions where multiple items are reviewed independently from each other.

In the reviewing step, display functions can be registered by card type. This allows easy addition of user-defined card types without having to think about storing and updating review data.

Review functions are called with point on the headline of the card that should be reviewed and get passed a single argument, the position to be reviewed.

They are expected to return either 'quit to end the review or one of 'again, 'hard, 'good, 'ease, to rate the card.

Design Goals / Choices

Use of awk for quickly finding cards due for review
Support for multiple positions in a card / heading
All relevant data kept in org files for easy version control
Review directly on the source org file for easy editing of cards during review

See Design Choices for more information.

Prior Art

There are a few other packages for implementing a SRS based on org-mode.

Below, I’ve listed a the ones I’ve found so far that are actively maintained and implement a lot of useful functionality.

phillord/org-drill
abo-abo/pamparam

Other (open source) flashcard / spaced repetition software:

Anki
Mnemosyne Project

Thanks to the maintainers and all contributors for their work on these packages!

Performance

All user-facing commands (especially during review) should be as fast as possible (<300ms).

Using the awk indexer, searching 2500 org files (~200k lines in total) for due flashcards takes around ~500ms on my laptop (Thinkpad L470, SSD).

Using the lisp indexer based on org-map-entries, searching a single 6500 line file with 333 flashcards takes ~1000ms, indexing the same file with awk takes around ~50ms.

Getting Started

Before using this package, org-fc-directories should be set to the directory to search for org files containing flashcards.

The file used to store the review history can be customized with org-fc-review-history-file and defaults to /path/to/config/org-fc-reviews.tsv.

This package is not (yet) available on MELPA / ELPA, to install it, clone the repository (e.g. to src/org-fc/) and follow the setup instructions.

Dependencies

The gawk extension of awk for extracting review data from .org files
find for finding all org files in the org-fc-directories
xargs for processing files in parallel

Linux / UNIX

find and xargs should be included in most distributions, gawk can be installed from source or using your package manager of choice.

Examples:

pacman -S gawk (Arch Linux)
apt-get install gawk (Ubuntu, Debian, …)
yum install gawk (CentOS)

For more information, see gawk manual - Installation.

MacOS

On MacOS all dependencies can be installed using macports or homebrew. find and xargs are part of the findutils package.

port install gawk findutils
brew install gawk findutils

You might have to adjust your $PATH to make sure Emacs can find all relevant binaries.

export PATH="/opt/local/libexec/gnubin:/opt/local/bin:$PATH"

For more information, refer to the documentation of macports / homebrew.

Setup with use-package

(use-package hydra)
(use-package org-fc
  :load-path "~/src/org-fc"
  :custom (org-fc-directories '("~/org/"))
  :config
  (require 'org-fc-hydra))

Or, using straight.el:

(use-package hydra)
(use-package org-fc
  :straight
  (org-fc
   :type git :host github :repo "l3kn/org-fc"
   :files (:defaults "awk" "demo.org"))
  :custom
  (org-fc-directories '("~/org/"))
  :config
  (require 'org-fc-hydra))

Note that in this case, you don’t have to clone the repository.

Setup with straight.el

(straight-use-package 'hydra)
(straight-use-package
 '(org-fc
   :type git :host github :repo "l3kn/org-fc"
   :files (:defaults "awk" "demo.org")
   :custom (org-fc-directories '("~/org/"))
   :config
   (require 'org-fc-hydra)))

Setup with spacemacs

You don’t need to manually clone the repository, just put this in your .spacemacs:

;; ...
dotspacemacs-additional-packages
'((org-fc
   :location (recipe :fetcher github
                     :repo "l3kn/org-fc"
                     :files (:defaults "awk" "demo.org"))))
;; ...
(defun dotspacemacs/user-config ()
  ;; ...
  ;; Org-fc
  (use-package hydra)
  (require 'org-fc-hydra)
  (setq org-fc-directories '("~/org/"))
  ;; ...
  )

Minimal Setup

Assuming abo-abo/hydra is already loaded.

(add-to-list 'load-path "~/src/org-fc/")
(setq org-fc-directories '("~/org/"))

Demo Mode

A file demonstrating all card types is included. M-x org-fc-demo starts a review of this file.

Card Types

This package comes with a few predefined card types. They are documented in Card Types.

demo.org includes examples for each of these types.

Marking Headlines as Cards

A card is an org-mode headline with a :fc: tag attached to it. Each card can have multiple positions reviewed independently from each other, e.g. one for each hole of a cloze card.

Review data (ease, interval in days, box, due date) is stored in a table in a drawer inside the card.

:REVIEW_DATA:
| position | ease | box | interval | due                    |
|----------+------+-----+----------+------------------------|
|        2 | 2.65 |   6 |   107.13 |    2020-04-07T01:01:00 |
|        1 | 2.65 |   6 |   128.19 |    2020-04-29T06:44:00 |
|        0 | 2.95 |   6 |   131.57 |    2020-04-30T18:03:00 |
:END:

Review results are appended to a csv file to avoid cluttering the org files.

Each card needs at least two properties, an unique :ID: and a :FC_TYPE:. In addition to that, the date a card was created (i.e. the headline was marked as a flashcard) is stored to allow making statistics for how many cards were created in the last day / week / month.

:PROPERTIES:
:ID:       4ffe66a7-7b5c-4811-bd3e-02b5c0862f55
:FC_TYPE:  normal
:FC_CREATED: 2019-10-11T14:08:32
:END:

Card types (should) implement a org-fc-type-...-init command that initializes these properties and sets up the review data drawer

All timestamps created and used by org-flashcards use ISO8601 format with second precision and without a timezone (timezone UTC0).

This prevents flashcard due dates from showing up in the org-agenda and allows filtering for due cards by string-comparing a timestamp with one of the current time.

(Un)suspending Cards

Cards can be suspended (excluded from review) by adding a suspended tag, either by hand or using the org-fc-suspend-card command.

All cards in the current buffer can be suspended using the org-fc-suspend-buffer command.

The reason for using a per-headline tag instead of a file keyword is that this way cards stay suspended when moved to another buffer.

Cards can be un-suspended using the org-fc-unsuspend-card and org-fc-unsuspend-buffer commands.

If the card being unsuspended was not due for review yet, or was due less than 10% of its interval ago, its review data is not reset. If it was due by more than that, its review data is reset to the initial values.

Spacing Algorithm

This package uses a modified version of the SM2 spacing algorithm, based on the one used by Anki.

Review

A review session can be started with M-x org-fc-review. Due cards are reviewed in random order.

If a card was rated “again”, it will be reviewed again at the end of the current review session. This can be disabled by setting org-fc-append-failed-cards to nil.

Review Process

Open file of card
Narrow to heading
Set up card for review
Activate org-fc-flip-mode
Flip the card (user)
Switch to org-fc-rate-mode
Rate the card (user)
Repeat process with next due card

Flip Mode

Key	Binding
RET	flip card
n	flip card
s	suspend card
p	pause review for editing
q	quit review

Rate Mode

Key	Binding
a	rate again
h	rate hard
g	rate good
e	rate easy
s	suspend card
p	pause review for editing
q	quit review

Use with `evil-mode`

The key bindings used by the review modes of org-fc conflict with some of the bindings used by evil mode.

As a workaround, you can add minor mode keymaps for each of the evil-mode states you’re using org-fc with.

(evil-define-minor-mode-key '(normal insert emacs) 'org-fc-review-flip-mode
  (kbd "RET") 'org-fc-review-flip
  (kbd "n") 'org-fc-review-flip
  (kbd "s") 'org-fc-review-suspend-card
  (kbd "q") 'org-fc-review-quit)

(evil-define-minor-mode-key '(normal insert emacs) 'org-fc-review-rate-mode
  (kbd "a") 'org-fc-review-rate-again
  (kbd "h") 'org-fc-review-rate-hard
  (kbd "g") 'org-fc-review-rate-good
  (kbd "e") 'org-fc-review-rate-easy
  (kbd "s") 'org-fc-review-suspend-card
  (kbd "q") 'org-fc-review-quit)

Review Contexts

By default, two contexts are defined:

all: all cards in org-fc-directories
buffer: all cards in the current buffer

New contexts can be defined by adding them to the alist org-fc-custom-contexts.

Contexts have the form (:paths paths :filter filter).

:paths (optional) either a list of paths, a single path or 'buffer for the current buffer. Paths don’t have to be included in the org-fc-directories. Defaults to org-fc-directories.
:filter (optional), a card filter defaulting to a filter that matches all cards.

Filters can be combinations of the following expressions:

(and ex1 ex2 ...)
(or ex1 ex2 ...)
(not ex)
(tag "tag")
(type card-type) or (type "card-type")

Examples

All double cards with tag “math”:

(add-to-list 'org-fc-custom-contexts
  '(double-math-cards . (:filter (and (type double) (tag "math")))))

All cards in that don’t have one of the tags “foo” and “bar”:

(add-to-list 'org-fc-custom-contexts
  '(no-foo-bar-cards . (:filter (not (or (tag "foo") (tag "bar"))))))

All cards in ~/combinatorics/ or ~/number_theory.org:

(add-to-list 'org-fc-custom-contexts
  '(math-cards . (:paths ("~/combinatorics/" "~/number_theory.org"))))

All cards in ~/combinatorics/ with tag “theorem”:

(add-to-list 'org-fc-custom-contexts
  '(combinatorics-theorems .
    (:paths "~/combinatorics/" :filter (tag "theorem"))))

All double cards in the current buffer:

(add-to-list 'org-fc-custom-contexts
  '(current-double .
    (:paths buffer :filter (type double))))

Note

Because parsing of tags is done in AWK, tag filters don’t work for tags defined in the #+FILETAGS: of a #+SETUP_FILE:.

Dashboard / Statistics

org-fc-dashboard shows a buffer with statistics for review performance and cards / card types.

Only cards with a box >= org-fc-stats-review-min-box (default: 0) are included in the review statistics.

Setting this to a higher value (e.g. 2) excludes the first few “learning” reviews of a card.

Hooks

org-fc-before-setup-hook Runs before a card is set up for review
org-fc-after-setup-hook Runs after a card is set up for review
org-fc-after-review-hook Runs when the review ends / is quit

Extensions

Org-fc comes with a number of extensions that are not enabled by default.

`org-fc-audio`

Can be enabled with (require 'org-fc-audio).

Adds audio attachments for cards that are played during review, either before or after a card is set up. (This distinction is relevant for text-input cards).

Commands:

org-fc-audio-set-before
org-fc-audio-set-after

`org-fc-keymap-hint`

Can be enabled with (require 'org-fc-keymap-hint).

Shows a list of available key bindings during the review, to recreate the look & feel of the previous hydra-based implementation.

[RET] flip [q] quit [s] suspend-card
[a] rate-again [h] rate-hard [g] rate-good [e] rate-easy [s] suspend-card [q] quit

`org-fc-hydra`

org-fc-hydra.el defines a hydra for accessing commonly used org-fc commands and for marking headlines as flashcards.

It can be loaded and bound to a hotkey like this:

(require 'org-fc-hydra)
(global-set-key (kbd "C-c f") 'org-fc-hydra/body)

Files

README.org

Latest commit

History