tco.js
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	import { test, summary } from './helpers.js';

	console.log('Tail Call Optimization Tests\n');

	function factorial(n, acc = 1) {
	if (n <= 1) return acc;
	return factorial(n - 1, n * acc);
	}
	test('tail factorial(10)', factorial(10), 3628800);
	test('tail factorial(20)', factorial(20), 2432902008176640000);

	function countDown(n) {
	if (n <= 0) return 'done';
	return countDown(n - 1);
	}
	test('deep tail recursion', countDown(100000), 'done');

	function sum(n, acc = 0) {
	if (n <= 0) return acc;
	return sum(n - 1, acc + n);
	}
	test('tail sum(100000)', sum(100000), 5000050000);

	function fib(n, a = 0, b = 1) {
	if (n === 0) return a;
	if (n === 1) return b;
	return fib(n - 1, b, a + b);
	}
	test('tail fib(10)', fib(10), 55);
	test('tail fib(30)', fib(30), 832040);

	function isEven(n) {
	if (n === 0) return true;
	return isOdd(n - 1);
	}
	function isOdd(n) {
	if (n === 0) return false;
	return isEven(n - 1);
	}
	test('mutual isEven(10)', isEven(10), true);
	test('mutual isOdd(11)', isOdd(11), true);
	test('mutual isEven(10000)', isEven(10000), true);

	function normalFib(n) {
	if (n <= 1) return n;
	return normalFib(n - 1) + normalFib(n - 2);
	}
	test('non-tail recursion', normalFib(10), 55);

	function normalFactorial(n) {
	if (n <= 1) return 1;
	return n * normalFactorial(n - 1);
	}
	test('non-tail factorial', normalFactorial(5), 120);

	function tailMultiArg(a, b, c) {
	if (a <= 0) return b + c;
	return tailMultiArg(a - 1, b + 1, c + 2);
	}
	test('tail multi-arg', tailMultiArg(1000, 0, 0), 3000);

	function ternaryTail(n) {
	return n <= 0 ? 'done' : ternaryTail(n - 1);
	}
	test('ternary tail', ternaryTail(50000), 'done');

	function lastElement(arr, i = 0) {
	if (i >= arr.length - 1) return arr[i];
	return lastElement(arr, i + 1);
	}
	test('tail lastElement', lastElement([1, 2, 3, 4, 5]), 5);

	function ternaryBothBare(n) {
	return n <= 0 ? ternaryBothBare_done(n) : ternaryBothBare(n - 1);
	}
	function ternaryBothBare_done(_) {
	return 'done';
	}
	test('ternary both bare calls', ternaryBothBare(100000), 'done');

	function ternaryThenBinop(n) {
	return n <= 0 ? identity(0) + 1 : ternaryThenBinop(n - 1);
	}
	function identity(x) {
	return x;
	}
	test('ternary then-branch binop', ternaryThenBinop(5), 1);

	function ternaryElseBinop(n) {
	return n <= 0 ? identity(42) : identity(n) * 2;
	}
	test('ternary else-branch binop', ternaryElseBinop(0), 42);
	test('ternary else-branch binop non-zero', ternaryElseBinop(3), 6);

	function ternaryBothBinop(n) {
	return n <= 0 ? identity(10) + 5 : identity(n) - 1;
	}
	test('ternary both branches binop', ternaryBothBinop(0), 15);
	test('ternary both branches binop non-zero', ternaryBothBinop(7), 6);

	function ternaryNestedArith(n) {
	return n <= 0 ? (identity(2) + 3) * identity(4) : ternaryNestedArith(n - 1);
	}
	test('ternary nested arith in then', ternaryNestedArith(5), 20);

	function ternaryParenBareCall(n) {
	return n <= 0 ? ternaryParenBareCall_end() : ternaryParenBareCall(n - 1);
	}
	function ternaryParenBareCall_end() {
	return 'end';
	}
	test('ternary paren bare call', ternaryParenBareCall(100000), 'end');

	function ternaryCallWithBinopArg(n) {
	return n <= 0 ? identity(2 + 3) : ternaryCallWithBinopArg(n - 1);
	}
	test('ternary call with binop arg', ternaryCallWithBinopArg(100000), 5);

	function ternaryNested(n, branch) {
	return branch === 0 ? ternaryNested_a(n) : branch === 1 ? ternaryNested_b(n) : ternaryNested_c(n);
	}
	function ternaryNested_a(_) {
	return 'a';
	}
	function ternaryNested_b(_) {
	return 'b';
	}
	function ternaryNested_c(_) {
	return 'c';
	}
	test('nested ternary branch 0', ternaryNested(1, 0), 'a');
	test('nested ternary branch 1', ternaryNested(1, 1), 'b');
	test('nested ternary branch 2', ternaryNested(1, 2), 'c');

	function ternaryNestedUnsafe(n, branch) {
	return branch === 0 ? identity(n) + 1 : branch === 1 ? identity(n) : identity(n) * 3;
	}
	test('nested ternary unsafe then', ternaryNestedUnsafe(5, 0), 6);
	test('nested ternary safe middle', ternaryNestedUnsafe(5, 1), 5);
	test('nested ternary unsafe else', ternaryNestedUnsafe(5, 2), 15);

	summary();

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