repro_bouncer_collectdecl.js
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repro_bouncer_collectdecl.js
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	const bouncer = (f, ini) => {
	let obj = ini;
	while (obj.tag) obj = f(obj);
	return obj.h0;
	};

	const Nil = { tag: 0 };
	const Cons = (h, t) => ({ tag: 1, h1: h, h2: t });

	function mkList(n) {
	let xs = Nil;
	for (let i = n; i > 0; i--) xs = Cons(i, xs);
	return xs;
	}

	const collectBad = xs => bouncer(collectBadREC, { tag: 1, h0: xs });
	const collectBadREC = arg => {
	if (arg.h0.tag === 1) {
	return { tag: 0, h0: Cons(arg.h0.h1, collectBad(arg.h0.h2)) };
	}
	return { tag: 0, h0: Nil };
	};

	const collectGood = xs => reverse(bouncer(collectGoodREC, { tag: 1, h0: xs, h1: Nil }));
	const collectGoodREC = arg => {
	if (arg.h0.tag === 1) return { tag: 1, h0: arg.h0.h2, h1: Cons(arg.h0.h1, arg.h1) };
	return { tag: 0, h0: arg.h1 };
	};

	function reverse(xs) {
	let out = Nil;
	while (xs.tag === 1) {
	out = Cons(xs.h1, out);
	xs = xs.h2;
	}
	return out;
	}

	const n = Number(process.argv[2] \|\| 5000);
	const xs = mkList(n);

	try {
	collectBad(xs);
	} catch {
	console.log('FAIL: collectBad should not overflow');
	process.exit(1);
	}

	collectGood(xs);
	console.log('PASS');