recursion works for types with depth limit 5

2 files changed, 26 insertions, 0 deletions

diff --git a/src/lang/ts-lang/util/number.ts b/src/lang/ts-lang/util/number.ts
index 6e4e360..2fa6d85 100644
--- a/src/lang/ts-lang/util/number.ts
+++ b/src/lang/ts-lang/util/number.ts
@@ -20,6 +20,18 @@ export type AddNumbers<Numbers extends readonly number[]> =
     ? T["length"]
     : never;
 
+export type SubNumbersInternal<
+  MS extends readonly unknown[],
+  NS extends readonly unknown[]
+> = MS extends readonly [...NS, ...infer Tail] ? Tail : never;
+
+export type SubNumbers<M extends number, N extends number> = SubNumbersInternal<
+  NumberToArray<M>,
+  NumberToArray<N>
+> extends infer T extends readonly any[]
+  ? T["length"]
+  : never;
+
 export type MultiplyInner<
   N extends number,
   MS extends readonly any[],
diff --git a/src/lang/ts-lang/util/utils.ts b/src/lang/ts-lang/util/utils.ts
index ac36ca1..d6d46f7 100644
--- a/src/lang/ts-lang/util/utils.ts
+++ b/src/lang/ts-lang/util/utils.ts
@@ -6,3 +6,17 @@ export type UnarrayIfOnlyHead<T extends readonly any[]> = T extends [
   : T extends [infer Head]
   ? Head
   : T;
+
+type ARR_EQUAL_SENTINEL = { __arrEq: true };
+export type ArrayEqual<
+  T extends readonly any[],
+  Last = ARR_EQUAL_SENTINEL
+> = T extends [infer Head, ...infer Tail]
+  ? Last extends ARR_EQUAL_SENTINEL
+    ? ArrayEqual<Tail, Head>
+    : Head extends Last
+    ? Last extends Head
+      ? ArrayEqual<Tail, Head>
+      : false
+    : false
+  : true;