Merge pull request #1008 from bmusin/patch-18

collapse two examples into one to simplify reading

Author: marioidival

src/std_misc/ffi.md

@@ -13,59 +13,26 @@ extern {
     // this is a foreign function
     // that computes the square root of a single precision complex number
     fn csqrtf(z: Complex) -> Complex;
-}
-
-fn main() {
-    // z = -1 + 0i
-    let z = Complex { re: -1., im: 0. };
 
-    // calling a foreign function is an unsafe operation
-    let z_sqrt = unsafe {
-        csqrtf(z)
-    };
-
-    println!("the square root of {:?} is {:?}", z, z_sqrt);
-}
-
-// Minimal implementation of single precision complex numbers
-#[repr(C)]
-#[derive(Clone, Copy)]
-struct Complex {
-    re: f32,
-    im: f32,
-}
-
-impl fmt::Debug for Complex {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        if self.im < 0. {
-            write!(f, "{}-{}i", self.re, -self.im)
-        } else {
-            write!(f, "{}+{}i", self.re, self.im)
-        }
-    }
-}
-```
-
-Since calling foreign functions is considered unsafe, it's common to write safe
-wrappers around them.
-
-```rust,ignore
-use std::fmt;
-
-#[link(name = "m")]
-extern {
     fn ccosf(z: Complex) -> Complex;
 }
 
-// safe wrapper
+// Since calling foreign functions is considered unsafe,
+// it's common to write safe wrappers around them.
 fn cos(z: Complex) -> Complex {
     unsafe { ccosf(z) }
 }
 
 fn main() {
-    // z = 0 + 1i
-    let z = Complex { re: 0., im: 1. };
+    // z = -1 + 0i
+    let z = Complex { re: -1., im: 0. };
+
+    // calling a foreign function is an unsafe operation
+    let z_sqrt = unsafe { csqrtf(z) };
+
+    println!("the square root of {:?} is {:?}", z, z_sqrt);
 
+    // calling safe API wrapped around unsafe operation
     println!("cos({:?}) = {:?}", z, cos(z));
 }