Extract SM2 code

1 files changed, 114 insertions, 0 deletions

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+;;; org-fc-algo-sm2.el --- Variation of SM2 spacing algorithm -*- lexical-binding: t; -*-
+
+;; Copyright (C) 2020  Leon Rische
+
+;; Author: Leon Rische <emacs@leonrische.me>
+
+;; This program is free software; you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; This program is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+;;; Commentary:
+;;
+;;
+;;
+;;; Code:
+
+;;;; Parameters
+
+(defcustom org-fc-algo-sm2-changes
+  '((again . -0.3)
+    (hard . -0.15)
+    (good . 0.0)
+    (easy . 0.15))
+  "Changes to a cards ease depending on its rating."
+  :type 'list
+  :group 'org-fc)
+
+(defcustom org-fc-algo-sm2-fixed-intervals
+  '(0.0 0.01 1.0 6.0)
+  "Hard-coded intervals for the first few card boxes.
+Values are in days."
+  :type 'list
+  :group 'org-fc)
+
+(defcustom org-fc-algo-sm2-ease-min 1.3 "Lower bound for a cards ease."
+  :type 'float
+  :group 'org-fc)
+
+(defcustom org-fc-algo-sm2-ease-initial 2.5 "Initial ease."
+  :type 'float
+  :group 'org-fc)
+
+(defcustom org-fc-algo-sm2-ease-max 5.0 "Upper bound for a cards ease."
+  :type 'float
+  :group 'org-fc)
+
+(defcustom org-fc-algo-sm2-fuzz-min 0.9
+  "Lower bound for random interval fuzz factor."
+  :type 'float
+  :group 'org-fc)
+
+(defcustom org-fc-algo-sm2-fuzz-max 1.1
+  "Upper bound for random interval fuzz factor."
+  :type 'float
+  :group 'org-fc)
+
+;;;; Helper Functions
+
+(defun org-fc-algo-sm2-fuzz (interval)
+  "Apply fuzz to INTERVAL.
+INTERVAL is by a random factor between `org-fc-sm2-fuzz-min' and
+`org-fc-sm2-fuzz-max'"
+  (*
+   interval
+   (+ org-fc-sm2-fuzz-min
+      (cl-random (- org-fc-sm2-fuzz-max org-fc-sm2-fuzz-min)))))
+
+;;;; Main Algorithm
+
+(defun org-fc-algo-sm2-next-parameters (ease box interval rating)
+  "Calculate the next parameters of a card, based on the review RATING.
+EASE, BOX and INTERVAL are the current parameters of the card."
+  (let* ((next-ease
+          (if (< box 2)
+              ease
+            (min
+             (max
+              (+ ease (alist-get rating org-fc-sm2-changes))
+              org-fc-sm2-ease-min)
+             org-fc-sm2-ease-max)))
+         (next-box
+          (cond
+           ;; If a card is rated easy, skip the learning phase
+           ((and (eq box 0) (eq rating 'easy)) 2)
+           ;; If the review failed, go back to box 0
+           ((eq rating 'again) 0)
+           ;; Otherwise, move forward one box
+           (t (1+ box))))
+         (next-interval
+          (cond ((< next-box (length org-fc-sm2-fixed-intervals))
+                 (nth next-box org-fc-sm2-fixed-intervals))
+                ((and (eq org-fc-algorithm 'sm2-v2) (eq rating 'hard)) (* 1.2 interval))
+                (t (org-fc-sm2-fuzz (* next-ease interval))))))
+    (list next-ease next-box next-interval)))
+
+(defun org-fc-algo-sm2-initial-review-data (position)
+  "Initial SM2 review data for POSITION."
+  (list position org-fc-sm2-ease-initial 0 0
+        (org-fc-timestamp-now)))
+
+;;; Footer
+
+(provide 'org-fc-algo-sm2)
+
+;;; org-fc-algo-sm2.el ends here