feat: more math & refactor

src/internal.ts

@@ -7,6 +7,10 @@ export interface Identity extends HKT {
 // eslint-disable-next-line @typescript-eslint/no-unsafe-type-assertion
 export const never = undefined as never;
 
+export function isArray(v: unknown): v is unknown[] {
+	return typeof v === "object" && v !== null && Array.isArray(v);
+}
+
 export class AssertionError extends Error {
 	public constructor(msg?: string) {
 		super(msg);
@@ -26,9 +30,11 @@ export function assert(
 		);
 }
 
-// eslint-disable-next-line @typescript-eslint/no-unnecessary-type-parameters, @typescript-eslint/no-unused-vars
-export function assertType<T>(_v: unknown): asserts _v is T {
-	/* empty */
+export namespace assert {
+	// eslint-disable-next-line @typescript-eslint/no-unused-vars
+	export function type<T>(_v: unknown): asserts _v is NoInfer<T> {
+		/* empty */
+	}
 }
 
 // eslint-disable-next-line @typescript-eslint/no-unsafe-function-type