在Rust中使用C语言的库功能

主要是了解unsafe{}语法块的作用。

#[repr(C)]
#[derive(Copy, Clone)]
#[derive(Debug)]
struct Complex {
  re: f32,
  im: f32,
}
#[link(name = "m")]
extern {
  fn ctanf(z: Complex) -> Complex;
}
fn tan(z: Complex) -> Complex {
  unsafe { ctanf(z) }
}
fn main() {
  let z = Complex { re: -., im: . }; // z is -1 + i
  let z_tan = tan(z);
  println!("the tangens of {:?} is {:?}", z, z_tan);
}