extract reason/

Author: xieyuheng

TODO.md

@@ -2,6 +2,7 @@
 
 > - https://github.com/cicada-lang/propagator/issues/3
 
+assertBeliefSystemReasons
 barometer-belief-system.test.ts -- finishing
 `beliefSystemQuery`
 

src/belief-system/beliefSystemMerge.ts

@@ -1,6 +1,7 @@
-import { Belief, isBelief, type Reasons } from "../belief/index.js"
+import { Belief, isBelief } from "../belief/index.js"
 import { isNothing, nothing, type Nothing } from "../cell/index.js"
 import { implies, merge, type MergeConflict } from "../merge/index.js"
+import type { Reasons } from "../reason/index.js"
 import { setIsSubsetOf } from "../utils/Set.js"
 import { BeliefSystem } from "./BeliefSystem.js"
 

src/belief/Belief.ts

@@ -1,19 +1,8 @@
 import assert from "node:assert"
+import { toReasons, type Reasons } from "../reason/index.js"
 import { isNonNullObject } from "../utils/isNonNullObject.js"
 import { log } from "../utils/log.js"
 
-export type Reason = string
-export type Reasons = Set<Reason>
-export type ReasonLike = Reasons | Array<Reason>
-
-export function toReason(x: ReasonLike): Reasons {
-  if (x instanceof Array) {
-    return new Set(x)
-  }
-
-  return x
-}
-
 export type Belief<T> = {
   "@type": "Belief"
   value: T
@@ -24,7 +13,7 @@ export function Belief<T>(
   value: T,
   reasons: Reasons | Array<string>,
 ): Belief<T> {
-  reasons = toReason(reasons)
+  reasons = toReasons(reasons)
 
   return {
     "@type": "Belief",
@@ -60,7 +49,7 @@ export function assertBeliefReasons(
   }
 
   if (reasons !== undefined) {
-    reasons = toReason(reasons)
+    reasons = toReasons(reasons)
 
     assert.deepStrictEqual(target.reasons, reasons)
   }

src/reason/Reason.ts

@@ -0,0 +1,11 @@
+export type Reason = string
+export type Reasons = Set<Reason>
+export type ReasonLike = Reasons | Array<Reason>
+
+export function toReasons(x: ReasonLike): Reasons {
+  if (x instanceof Array) {
+    return new Set(x)
+  }
+
+  return x
+}

src/reason/index.ts

@@ -0,0 +1 @@
+export * from "./Reason.js"