add S-expression example

examples/s-expression.test.ts

@@ -0,0 +1,22 @@
+import { describe, expect, test } from "@jest/globals";
+import { EOI } from "../src";
+import { SExpression } from "./s-expression";
+
+describe("S-expression", () => {
+    test("Hello world!", () => {
+        const source = '(print "Hello world!")';
+        expect(SExpression.skip(EOI).parse(source)).toEqual({
+            success: true,
+            index: expect.any(Number),
+            value: ["print", '"Hello world!"'],
+        });
+    });
+    test("quote list", () => {
+        const source = "'(1 2 3 4)";
+        expect(SExpression.skip(EOI).parse(source)).toEqual({
+            success: true,
+            index: expect.any(Number),
+            value: ["quote", "1", "2", "3", "4"],
+        });
+    });
+});

examples/s-expression.ts

@@ -0,0 +1,16 @@
+import { type Parser, choice, el, lazy, many, regex } from "../src";
+
+export type SExpression = string | readonly SExpression[];
+
+const list = lazy(() => SExpression)
+    .apply(many)
+    .between(el("("), el(")"));
+
+export const SExpression: Parser<SExpression, string> = choice([
+    el("'")
+        .option()
+        .and(list)
+        .map(([quote, list]) => (quote ? ["quote", ...list] : list)),
+    regex(/"([^"]|\\.)*"/),
+    regex(/[^\s()"]+/),
+]).between(regex(/\s*/));