Rust Essentials - Second Edition

Using a C library

Suppose we want to calculate the tangents of a complex number. The num crate offers this functionality; however, for the purposes of this exercise, we will call the ctanf function from the C library libm instead. This is a collection of mathematical functions implemented in C. The following code defines a complex number as a simple struct.

Warning: This code only works on OS X and Linux, not on Windows.

// code from Chapter 10/code/calling_clibrary.rs: 
#[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: -1., im: 1. }; // z is -1 + i let ...