+TITLE: LISP-FSRS

[[https://melpa.org/#/fsrs][file:https://melpa.org/packages/fsrs-badge.svg]]

Implementation of the FSRS algorithm in Common Lisp and auto-transpiled to Emacs Lisp.

• Usage ** Common Lisp

  +BEGIN_SRC lisp

  CL-USER> (ql:quickload :lisp-fsrs) ; Ensure you have cloned this repository into the `local-projects' directory under your Quicklisp installation root. To load "lisp-fsrs": Load 1 ASDF system: lisp-fsrs ; Loading "lisp-fsrs" (:LISP-FSRS) CL-USER> (defparameter parameters (coerce '(0.2172 1.1771 3.2602 16.1507 7.0114 0.57 2.0966 0.0069 1.5261 0.112 1.0178 1.849 0.1133 0.3127 2.2934 0.2191 3.0004 0.7536 0.3332 0.1437 0.2) 'fsrs:parameters)) ,PARAMETERS CL-USER> (defparameter scheduler (fsrs:make-scheduler :parameters parameters)) ,SCHEDULER CL-USER> (defparameter card (fsrs:make-card)) ,CARD CL-USER> card

  S(LISP-FSRS:CARD

  :CARD-ID 0 :STATE :LEARNING :STEP 0 :STABILITY NIL :DIFFICULTY NIL :DUE @2025-06-08T13:39:42.230941+08:00 :LAST-REVIEW NIL) CL-USER> (setf card (fsrs:scheduler-review-card scheduler card :good))

  S(LISP-FSRS:CARD

  :CARD-ID 0 :STATE :LEARNING :STEP 1 :STABILITY 3.2602 :DIFFICULTY 4.884632 :DUE @2025-06-08T13:49:49.476969+08:00 :LAST-REVIEW @2025-06-08T13:39:49.476969+08:00) CL-USER> (setf card (fsrs:scheduler-review-card scheduler card :good))

  S(LISP-FSRS:CARD

  :CARD-ID 0 :STATE :REVIEW :STEP NIL :STABILITY 3.5362437 :DIFFICULTY 4.8680573 :DUE @2025-06-12T13:39:50.242969+08:00 :LAST-REVIEW @2025-06-08T13:39:50.242969+08:00)

  +END_SRC

To generate the ~fsrs~ package for Emacs after changing the code, ensure you are running the current Lisp session using ~sly~ in Emacs, then:

+BEGIN_SRC lisp

CL-USER> (ql:quickload :lisp-fsrs/emacs) To load "lisp-fsrs/emacs": Load 1 ASDF system: lisp-fsrs/emacs ; Loading "lisp-fsrs/emacs" [package lisp-fsrs.emacs].. (:LISP-FSRS/EMACS) CL-USER> (fsrs.emacs:translate-system) NIL

+END_SRC

** Emacs Lisp

+BEGIN_SRC emacs-lisp

ELISP> (package-vc-install "https://github.com/open-spaced-repetition/lisp-fsrs.git") t ELISP> (setq fsrs-parameters [0.2172 1.1771 3.2602 16.1507 7.0114 0.57 2.0966 0.0069 1.5261 0.112 1.0178 1.849 0.1133 0.3127 2.2934 0.2191 3.0004 0.7536 0.3332 0.1437 0.2]) [0.2172 1.1771 3.2602 16.1507 7.0114 0.57 2.0966 0.0069 1.5261 0.112 1.0178 1.849 0.1133 0.3127 2.2934 0.2191 3.0004 0.7536 0.3332 0.1437 0.2]

ELISP> (setq fsrs-scheduler (fsrs-make-scheduler))

s(fsrs-scheduler :parameters

                [0.2172 1.1771 3.2602 16.1507 7.0114 0.57 2.0966
                        0.0069 1.5261 0.112 1.0178 1.849 0.1133
                        0.3127 2.2934 0.2191 3.0004 0.7536 0.3332
                        0.1437 0.2]
                :desired-retention 0.9 :learning-steps
                ((1 :minute) (10 :minute)) :relearning-steps
                ((10 :minute)) :maximum-interval (36500 :day)
                :enable-fuzzing-p t)

ELISP> (setq fsrs-card (fsrs-make-card))

s(fsrs-card :card-id 0 :state :learning :step 0 :stability nil

           :difficulty nil :due "2025-06-08T05:38:50Z" :last-review
           nil)

ELISP> (setq fsrs-card (cl-nth-value 0 (fsrs-scheduler-review-card fsrs-scheduler fsrs-card :good)))

s(fsrs-card :card-id 0 :state :learning :step 1 :stability 3.2602

           :difficulty 4.884631634813845 :due "2025-06-08T05:48:52Z"
           :last-review "2025-06-08T05:38:52Z")

ELISP> (setq fsrs-card (cl-nth-value 0 (fsrs-scheduler-review-card fsrs-scheduler fsrs-card :good)))

s(fsrs-card :card-id 0 :state :review :step nil :stability

           3.536243655619573 :difficulty 4.868056502338024 :due
           "2025-06-10T05:38:53Z" :last-review
           "2025-06-08T05:38:53Z")

+END_SRC