Feat/calc s inc based on last_d (#59)

* Feat/calc SInc based on last_d

* 3.2.0

example/example.html

@@ -9,7 +9,7 @@
     <script src="https://unpkg.com/babel-standalone@6/babel.min.js"></script>
     <script src="https://cdn.tailwindcss.com?plugins=forms,typography,aspect-ratio,line-clamp"></script>
     <script type="module">
-        import * as tsFsrs from 'https://cdn.jsdelivr.net/npm/ts-fsrs@3.1.2/+esm';
+        import * as tsFsrs from 'https://cdn.jsdelivr.net/npm/ts-fsrs@3.2.0/+esm';
         window.tsfsrs = tsFsrs
     </script>
     <title>TS-FSRS example</title>

package.json

@@ -1,6 +1,6 @@
 {
   "name": "ts-fsrs",
-  "version": "3.1.3",
+  "version": "3.2.0",
   "description": "ts-fsrs is a TypeScript package used to implement the Free Spaced Repetition Scheduler (FSRS) algorithm. It helps developers apply FSRS to their flashcard applications, thereby improving the user learning experience.",
   "main": "dist/ts-fsrs.js",
   "module": "dist/ts-fsrs.mjs",

src/fsrs/algorithm.ts

@@ -44,27 +44,27 @@ export class FSRSAlgorithm {
   ): void {
     s.again.difficulty = this.next_difficulty(last_d, Rating.Again);
     s.again.stability = this.next_forget_stability(
-      s.again.difficulty,
+      last_d,
       last_s,
       retrievability,
     );
     s.hard.difficulty = this.next_difficulty(last_d, Rating.Hard);
     s.hard.stability = this.next_recall_stability(
-      s.hard.difficulty,
+      last_d,
       last_s,
       retrievability,
       Rating.Hard,
     );
     s.good.difficulty = this.next_difficulty(last_d, Rating.Good);
     s.good.stability = this.next_recall_stability(
-      s.good.difficulty,
+      last_d,
       last_s,
       retrievability,
       Rating.Good,
     );
     s.easy.difficulty = this.next_difficulty(last_d, Rating.Easy);
     s.easy.stability = this.next_recall_stability(
-      s.easy.difficulty,
+      last_d,
       last_s,
       retrievability,
       Rating.Easy,

src/fsrs/default.ts

@@ -9,7 +9,7 @@ export const default_w = [
 ];
 export const default_enable_fuzz = false;
 
-export const FSRSVersion: string = "3.1.3";
+export const FSRSVersion: string = "3.2.0";
 
 export const generatorParameters = (
   props?: Partial<FSRSParameters>,