move generic method to IterableResult

Author: neverRare

src/compound.ts

@@ -137,6 +137,24 @@ export class IterableResult<T> {
     ) as IterableResult<T>;
   }
 
+  static combinationOnTwo<T>(
+    array: ReadonlyArray<T>,
+  ): IterableResult<readonly [ReadonlyArray<T>, ReadonlyArray<T>]> {
+    if (array.length == 0) {
+      return IterableResult.single([[], []]);
+    } else {
+      const init = array.slice(0, array.length - 1);
+      const last = array[array.length - 1];
+      return IterableResult.combinationOnTwo(init)
+        .flatMap(([left, right]) =>
+          IterableResult.fromArray([
+            [[...left, last], right],
+            [left, [...right, last]],
+          ])
+        );
+    }
+  }
+
   static handleThrows<T>(
     iterableResult: () => IterableResult<T>,
   ): IterableResult<T> {

src/translator2/adjective.ts

@@ -4,7 +4,6 @@ import { nullableAsArray } from "../misc/misc.ts";
 import * as TokiPona from "../parser/ast.ts";
 import * as English from "./ast.ts";
 import { UntranslatableError } from "./error.ts";
-import { combinationOnTwo } from "./modifier.ts";
 import { noEmphasis, word } from "./word.ts";
 
 export type AdjectiveWithInWay = Readonly<{
@@ -113,12 +112,13 @@ export function shareAdverb(
 > {
   switch (adjective.type) {
     case "simple":
-      return combinationOnTwo(adjective.adverbs).map<
-        readonly [English.AdjectivePhrase, ReadonlyArray<English.Adverb>]
-      >(([forAdjective, forAdverb]) => [
-        { ...adjective, adverbs: forAdjective },
-        forAdverb,
-      ]);
+      return IterableResult.combinationOnTwo(adjective.adverbs)
+        .map<readonly [English.AdjectivePhrase, ReadonlyArray<English.Adverb>]>(
+          ([forAdjective, forAdverb]) => [
+            { ...adjective, adverbs: forAdjective },
+            forAdverb,
+          ],
+        );
     case "compound":
       return IterableResult.single<
         readonly [English.AdjectivePhrase, ReadonlyArray<English.Adverb>]

src/translator2/modifier.ts

@@ -273,7 +273,7 @@ export function multipleModifiers(
   modifiers: ReadonlyArray<TokiPona.Modifier>,
 ): IterableResult<MultipleModifierTranslation> {
   return IterableResult.combine(...modifiers.map(modifier))
-    .flatMap(combinationOnTwo)
+    .flatMap(IterableResult.combinationOnTwo)
     .filterMap(([forAdjectival, forAdverbial]) => {
       const adjectival = adjectivalModifier(forAdjectival);
       const adverbial = adverbialModifier(forAdverbial);
@@ -287,21 +287,3 @@ export function multipleModifiers(
       new ExhaustedError(modifiers.map(Composer.modifier).join(" "))
     );
 }
-// TODO: move this as IterableResult static method
-export function combinationOnTwo<T>(
-  array: ReadonlyArray<T>,
-): IterableResult<readonly [ReadonlyArray<T>, ReadonlyArray<T>]> {
-  if (array.length == 0) {
-    return IterableResult.single([[], []]);
-  } else {
-    const init = array.slice(0, array.length - 1);
-    const last = array[array.length - 1];
-    return combinationOnTwo(init)
-      .flatMap(([left, right]) =>
-        IterableResult.fromArray([
-          [[...left, last], right],
-          [left, [...right, last]],
-        ])
-      );
-  }
-}