From JavaScript​

var x = 5;
x = "five";                  // var holds anything
auto n = 5;                  // inferred once: an int from here on
int hp = 10;
float speed = 2.5;
string name = "Ada";
print(type_of(x), " ", type_of(n), " ", type_of(speed), " ", type_of(null));
print(7 / 2, " ", 7.0 / 2, " ", 7 / 2.0);

function add(a, b) { return a + b; }
int add_ints(int a, int b) { return a + b; }
function hit(int dmg = 5) { return dmg; }
var f = add;
auto twice = x => x * 2;

int total = 0;                                    // a program-scope variable
function bank(int n) { total += n; }              // read and written when bank runs

function make_counter() {
    int count = 0;
    return [&]() { count += 1; return count; };   // [&] shares count with the closure
}
auto next = make_counter();
next();
bank(5);
bank(2);
print(f(1, 2), " ", add_ints(2, 3), " ", hit(), " ", hit(9), " ", twice(21), " ", next(), " ", total);

auto nums = [5, 3, 8, 1];
nums.push(4);
print(nums.size(), " ", nums.index_of(8), " ", nums.contains(7), " ", to_json(array::slice(nums, 1, 3)));
auto big = array::filter(nums, x => x > 3);
big.sort();
print(to_json(big), " ", big.join("-"));
int dbl(int v) { return v * 2; }
print(to_json(array::map(nums, dbl)));

var hero = {"hp": 10, "name": "Ada"};
hero["hp"] = 15;
hero["level"] = 2;
hero.erase("name");
print(to_json(hero), " ", hero.contains("hp"), " ", to_json(hero.keys()));

var inventory = {"potion": 3, "arrow": 20};
for (auto [item, count] : inventory) { print(item, " x", count); }
var names = ["ada", "bo"];
for (auto& n : names) { n = n + "!"; }
print(names.join(" "));

class Hero {
private:
    int gold = 0;
public:
    static int count = 0;
    string name;
    int hp = 10;
    Hero(string n) { name = n; Hero::count += 1; }
    string describe() { return name + " (" + hp + " hp)"; }
    int _get_wealth() { return gold; }
    void _set_wealth(int v) { gold = v < 0 ? 0 : v; }
}
class Mage : Hero {
    int mana = 30;
    Mage(string n) : super(n) {}
    string describe() override { return super::describe() + " with " + mana + " mana"; }
}
auto a = Hero("Ada");
auto m = Mage("Merlin");
a.wealth = 120;
m.wealth = -5;
print(a.describe());
print(m.describe());
print(a.wealth, " ", m.wealth, " ", Hero::count);

class Guard {
    string what;
    Guard(string w) { what = w; }
    ~Guard() { print("released ", what); }
}
function load(string path) {
    Guard g = Guard(path);
    throw "missing " + path;
}
try { load("level.dat"); } catch (e) {
    print("caught: ", e, " (line ", e.line, ", value ", e.value, ")");
}
var hp = 72.25;
var who = null;
print(`hp ${hp:.1f}`, " ", "42".to_int() + 1, " ", "ten".to_int() == null, " ", who?.size() == null);
print(who ?? "none", " ", string::to_upper("quiet"));

import "geometry.jai";

coroutine countdown(int from) {
    for (int i = from; i > 0; i--) { yield i; }
}
for (auto n : countdown(3)) { print("T-", n); }

var data = from_json("{\"name\": \"Ada\", \"tags\": [\"fast\", \"kind\"]}");
print(data["tags"][1], " ", area(3, 4), " ", math::floor(2.7), " ", cast<int>(2.7));
print(to_json({"w": 3, "h": 4}));

int area(int w, int h) { return w * h; }

var a = [1, 2, 3];
var b = a;                     // a copy
b.push(4);

class Hero { int hp = 10; }
Hero h = Hero();
Hero other = h;                // a copy too
other.hp = 1;

shared_ptr<Hero> s = new Hero();
auto alias = s;                // a handle: both names reach one object
alias.hp = 99;

function add_item(var& list, string item) { list.push(item); }
var bag = [];
add_item(bag, "rope");         // a reference parameter reaches the caller's array
print(a.size(), " ", b.size(), " ", h.hp, " ", s.hp, " ", bag.size());

print([1, 2] == [1, 2], " ", {"a": 1} == {"a": 1});
var a = [1, 2];
var b = a;
print(same_object(a, b));      // b is a separate array with equal contents
var one = "1";
print(1 == one, " ", 1 == 1.0);   // a var operand: false, never a conversion

print(7 / 2, " ", 7 / 2.0, " ", 0.1 + 0.2);
int big = 9223372036854775807;
try { big += 1; } catch (e) { print("caught: ", e); }
try { print(1 / 0); } catch (e) { print("caught: ", e); }

print("hp: " + 10, " / ", 1 + "0", " / ", "v" + 1 + 2);
string label = "hp: ";
var n = 10;
try { label += n; } catch (e) { print("caught: ", e); }
label += to_string(n);
print(label);

var values = [0, 0.0, "", [], {}, null, "0", [0]];
for (var v : values) { print("{} {}", to_json(v), v ? "true" : "false"); }

function ranks(int level) {
    string t = "";
    switch (level) {
        case 1: t += "novice ";
        case 2:
            t += "adept ";
            fallthrough;
        case 3: t += "master";
    }
    return t;
}
print("[", ranks(1), "] [", ranks(2), "]");

string name = "ada";
string shout = name.to_upper();          // name changes too
print(name, " ", shout);
string quiet = "BOB";
print(string::to_lower(quiet), " ", quiet);

var key = "speed";
var stats = {speed: 3, hp: 10};          // the keys "speed" and "hp"
stats[key] = 4;
print(to_json(stats), " ", stats["mana"] == null, " ", stats.size());
print(stats.hp);
try { stats.hp = 1; } catch (e) { print("caught: ", e); }

var a = [1, 2, 3, 4];
print(to_json(array::map(a, x => x * 2)), " ", a.reduce((sum, x) => sum + x, 0), " ", a.find(x => x > 2));
print(a.find_index(x => x > 9), " ", a.some(x => x > 3), " ", a.every(x => x > 0));
a.for_each((x, i) => print(i, "=", x));
var b = array::concat(a, [5]);
b.insert(0, 0);
print(to_json(b), " ", to_json(a));

function make_counter() {
    int count = 0;
    return function() { count += 1; return count; };
}
var next = make_counter();
next();
print(next());

function broken() {
    int count = 0;
    return []() { return count; };
}

var callbacks = [];
for (int i = 0; i < 3; i++) { callbacks.push([i]() { return i; }); }
for (auto cb : callbacks) { print(cb()); }

print(double_it(4));
function double_it(int x) { return x * 2; }

var a = [1, "two"];
print(a);
print(to_json(a));
print("{} and {}", 1, "two");
print(1, 2, 3);
var empty = {};
print(to_json(empty), " entries");         // "{}" is read as a placeholder
print("{} entries", to_json(empty));
class Tag { string to_string() { return "<tag>"; } }
print(Tag());

class QuestLog {
    var quests = {};                          // quest name -> progress
    array<function> listeners = [];

    void on_change(function f) { listeners.push(f); }

    void advance(string name, int by) {
        int now = quests.contains(name) ? quests[name] + by : by;
        quests[name] = now;
        for (auto& f : listeners) { f(name, now); }
    }
}

shared_ptr<QuestLog> journal = new QuestLog();      // one shared object, like a JavaScript object
array<string> messages = [];
journal.on_change([](string name, int progress) {
    messages.push(`${name}: ${progress}%`);         // messages is program scope: read when the listener runs
});

coroutine events() {
    yield ["rats", 50];
    yield ["relic", 25];
    yield ["rats", 50];
}
for (auto ev : events()) { journal.advance(ev[0], ev[1]); }

var done = [];
for (auto kv : journal.quests) {
    if (kv.second >= 100) { done.push(kv.first); }
}
print(messages.join(" | "));
print("done: ", done.join(", "));
print(to_json(journal.quests));