test_calls.dry

def test_function_partial_application() {
    let sum = lambda(x, y) { return x + y; };
    let onePlus = sum(1, _);

    assert_equals("Supply first function arg only", onePlus(3), 4);
    assert_equals("Supply second function arg only", sum(_, 3)(7), 10);
}

def test_method_partial_application() {
    class HasMinus {
        def minus(x, y) {
            return x - y;
        }
    }

    let tenMinus = HasMinus().minus(10, _);

    assert_equals("Supply first method arg only", tenMinus(6), 4);
    assert_equals("Supply second method arg only", HasMinus().minus(_, 4)(15), 11);
}

def test_non_callable() {
    assert_error_type("true is not callable", NotCallableError, lambda() { true(); });
    assert_error_type("none is not callable", NotCallableError, lambda() { none(); });
    assert_error_type("A number is not callable", NotCallableError, lambda() { 123(); });
    assert_error_type("A class instance is not callable", NotCallableError, lambda() {
        class Foo {}
        let foo = Foo();
        foo();
    });
    assert_error_type("A string is not callable", NotCallableError, lambda() { "str"(); });
}

test_function_partial_application();
test_method_partial_application();
test_non_callable();