定义 generateConceptSetByMeet 然后测试两种计算方式相等

Author: xieyuheng

TODO.md

@@ -1,5 +1,3 @@
-定义 `generateConceptSetByMeet` 然后测试两种计算方式相等
-
 # learn
 
 回顾《Restructuring lattice theory》笔记

src/lattice/generate-by-join-and-meet-are-the-same.test.ts

@@ -0,0 +1,27 @@
+import assert from "node:assert"
+import test from "node:test"
+import { createContextFromCrossTable } from "../context/createContextFromCrossTable.js"
+import { planets } from "../examples/planets.js"
+import { waterbodies } from "../examples/waterbodies.js"
+import { generateConceptSetByJoin } from "./generateConceptSetByJoin.js"
+import { generateConceptSetByMeet } from "./generateConceptSetByMeet.js"
+
+test("by join and meet are the same -- planets", () => {
+  const context = createContextFromCrossTable(planets)
+
+  assert(
+    generateConceptSetByJoin(context).isEqualTo(
+      generateConceptSetByMeet(context),
+    ),
+  )
+})
+
+test("by join and meet are the same -- waterbodies", () => {
+  const context = createContextFromCrossTable(waterbodies)
+
+  assert(
+    generateConceptSetByJoin(context).isEqualTo(
+      generateConceptSetByMeet(context),
+    ),
+  )
+})

src/lattice/generateConceptSetByMeet.ts

@@ -0,0 +1,29 @@
+import { conceptMeet, type Concept } from "../concept/index.js"
+import type { Context } from "../context/index.js"
+import type { QuotientSet } from "../utils/QuotientSet.js"
+import { generateAttributeConceptSet } from "./generateAttributeConceptSet.js"
+import { generateEntityConceptSet } from "./generateEntityConceptSet.js"
+
+export function generateConceptSetByMeet(
+  context: Context,
+): QuotientSet<Concept> {
+  const targets = generateAttributeConceptSet(context)
+  const results = generateEntityConceptSet(context).union(targets)
+
+  while (true) {
+    const first = targets.representatives.shift()
+    if (first === undefined) {
+      break
+    }
+
+    for (const target of targets.representatives) {
+      const concept = conceptMeet(first, target)
+      if (!results.has(concept)) {
+        targets.add(concept)
+        results.add(concept)
+      }
+    }
+  }
+
+  return results
+}

src/utils/QuotientSet.ts

@@ -52,4 +52,10 @@ export class QuotientSet<T> {
     for (const x of this.representatives) if (that.has(x)) newSet.add(x)
     return newSet
   }
+
+  isEqualTo(that: QuotientSet<T>): boolean {
+    if (this.equal !== that.equal) return false
+
+    return this.union(that).size === this.size
+  }
 }