How can I generate a random number?

I tried

use std::rand::{task_rng, Rng};

fn main() {
    // a number from [-40.0, 13000.0)
    let num: f64 = task_rng().gen_range(-40.0, 1.3e4);
    println!("{}", num);
}

but this gives

rust.rs:1:17: 1:25 error: unresolved import `std::rand::task_rng`. There is no `task_rng` in `std::rand`
rust.rs:1 use std::rand::{task_rng, Rng};
                          ^~~~~~~~
error: aborting due to previous error

and I tried

extern crate rand;
use rand::Rng;

fn main() {
    let mut rng = rand::thread_rng();
    if rng.gen() { // random bool
        println!("i32: {}, u32: {}", rng.gen::<i32>(), rng.gen::<u32>())
    }
    let tuple = rand::random::<(f64, char)>();
    println!("{:?}", tuple)
}

and got

rust.rs:5:19: 5:35 error: unresolved name `rand::thread_rng`
rust.rs:5     let mut rng = rand::thread_rng();
                            ^~~~~~~~~~~~~~~~
rust.rs:9:17: 9:44 error: unresolved name `rand::random`
rust.rs:9     let tuple = rand::random::<(f64, char)>();
                          ^~~~~~~~~~~~~~~~~~~~~~~~~~~
error: aborting due to 2 previous errors

I am using Rust 1.0.0-dev.