From 2927097382be5aad0b3737c2a70d544a8a030f2e Mon Sep 17 00:00:00 2001
From: Jim Blandy <jimb@red-bean.com>
Date: Sun, 6 Jun 2021 20:10:12 -0700
Subject: [PATCH] complex: Update for 2nd edition.

---
 complex/Cargo.toml |   1 +
 complex/src/lib.rs | 364 +++++++++++++++++++++++++++------------------
 2 files changed, 221 insertions(+), 144 deletions(-)

diff --git a/complex/Cargo.toml b/complex/Cargo.toml
index f95d50b..5f63568 100644
--- a/complex/Cargo.toml
+++ b/complex/Cargo.toml
@@ -2,5 +2,6 @@
 name = "complex"
 version = "0.1.0"
 authors = ["You <you@example.com>"]
+edition = "2018"
 
 [dependencies]
diff --git a/complex/src/lib.rs b/complex/src/lib.rs
index f04c050..1bc039d 100644
--- a/complex/src/lib.rs
+++ b/complex/src/lib.rs
@@ -1,192 +1,268 @@
-#[derive(Clone, Copy, Debug)]
-struct Complex<T> {
-    /// Real portion of the complex number
-    re: T,
+//! Complex number examples.
+//!
+//! The chapter presents several different variations on how one might define
+//! arithmetic on a generic `Complex` type, so what we have here are a bunch of
+//! isolated modules, each of which defines its own `Complex` type in its own
+//! way. The `first_cut` module is the most well-developed.
+//!
+//! If you actually need a `Complex` type for real use, consider the
+//! `num_complex` crate, whose `Complex` type is incorporated into the `num`
+//! crate.
 
-    /// Imaginary portion of the complex number
-    im: T
+macro_rules! define_complex {
+    () => {
+        #[derive(Clone, Copy, Debug)]
+        struct Complex<T> {
+            /// Real portion of the complex number
+            re: T,
+
+            /// Imaginary portion of the complex number
+            im: T,
+        }
+    };
 }
 
-use std::ops::Add;
-use std::ops::Mul;
+mod first_cut {
+    #[derive(Clone, Copy, Debug)]
+    struct Complex<T> {
+        /// Real portion of the complex number
+        re: T,
 
-#[cfg(skip)]
-impl Add for Complex<i32> {
-    type Output = Complex<i32>;
-    fn add(self, rhs: Self) -> Self {
-        Complex { re: self.re + rhs.re, im: self.im + rhs.im }
+        /// Imaginary portion of the complex number
+        im: T,
     }
-}
 
-impl<T> Add for Complex<T>
-    where T: Add<Output=T>
-{
-    type Output = Self;
-    fn add(self, rhs: Self) -> Self {
-        Complex { re: self.re + rhs.re, im: self.im + rhs.im }
+    use std::ops::Add;
+
+    impl<T> Add for Complex<T>
+    where
+        T: Add<Output = T>,
+    {
+        type Output = Self;
+        fn add(self, rhs: Self) -> Self {
+            Complex {
+                re: self.re + rhs.re,
+                im: self.im + rhs.im,
+            }
+        }
     }
-}
 
-#[cfg(skip)]
-impl<L, R, O> Add<Complex<R>> for Complex<L>
-    where L: Add<R, Output=O>
-{
-    type Output = Complex<O>;
-    fn add(self, rhs: Complex<R>) -> Self::Output {
-        Complex { re: self.re + rhs.re, im: self.im + rhs.im }
+    use std::ops::Sub;
+
+    impl<T> Sub for Complex<T>
+    where
+        T: Sub<Output = T>,
+    {
+        type Output = Self;
+        fn sub(self, rhs: Self) -> Self {
+            Complex {
+                re: self.re - rhs.re,
+                im: self.im - rhs.im,
+            }
+        }
     }
-}
 
-#[cfg(skip)]
-impl<'a, P, Rhs> Add for &'a Complex<P>
-    where P: Add<Output=P>,
-          Rhs: AsRef<Complex<P>>
-{
-    type Output = Complex<P>;
-    fn add(self, rhs: Rhs) -> Self::Output {
-        let rhs = rhs.as_ref();
-        Complex { re: self.re + rhs.re, im: self.im + rhs.im }
+    use std::ops::Mul;
+
+    impl<T> Mul for Complex<T>
+    where
+        T: Clone + Add<Output = T> + Sub<Output = T> + Mul<Output = T>,
+    {
+        type Output = Self;
+        fn mul(self, rhs: Self) -> Self {
+            Complex {
+                re: self.re.clone() * rhs.re.clone()
+                    - (self.im.clone() * rhs.im.clone()),
+                im: self.im * rhs.re + self.re * rhs.im,
+            }
+        }
+    }
+
+    #[test]
+    fn try_it_out() {
+        let mut z = Complex { re: 1, im: 2 };
+        let c = Complex { re: 3, im: 4 };
+
+        z = z * z + c;
+
+        std::mem::forget(z);
     }
-}
 
-use std::ops::Sub;
+    impl<T: PartialEq> PartialEq for Complex<T> {
+        fn eq(&self, other: &Complex<T>) -> bool {
+            self.re == other.re && self.im == other.im
+        }
+    }
 
-impl<T> Mul<Complex<T>> for Complex<T>
-    where T: Add<Output=T> + Sub<Output=T> + Mul<Output=T> + Copy
-{
-    type Output = Self;
-    fn mul(self, rhs: Self) -> Self {
-        Complex { re: self.re * rhs.re - self.im * rhs.im,
-                  im: self.re * rhs.im + self.im * rhs.re }
+    #[test]
+    fn test_complex_eq() {
+        let x = Complex { re: 5, im: 2 };
+        let y = Complex { re: 2, im: 5 };
+        assert_eq!(x * y, Complex { re: 0, im: 29 });
     }
-}
 
-#[test]
-fn test() {
-    let z = Complex { re: -2, im: 6 };
-    let c = Complex { re:  1, im: 2 };
-    assert_eq!(z + c,    Complex { re: -1, im: 8 });
-    assert_eq!(z * c,    Complex { re: -14, im: 2 });
-    assert_eq!(z.add(c), Complex { re: -1, im: 8 });
+    impl<T: Eq> Eq for Complex<T> {}
 }
 
-#[test]
-fn test_explicit() {
-    use std::ops::Add;
+mod non_generic_add {
+    define_complex!();
 
-    assert_eq!(4.125f32.add(5.75), 9.875);
-    assert_eq!(10.add(20), 10 + 20);
-}
+    use std::ops::Add;
 
-impl Add<Complex<f64>> for f64 {
-    type Output = Complex<f64>;
-    fn add(self, rhs: Complex<f64>) -> Complex<f64> {
-        Complex { re: rhs.re + self, im: rhs.im }
+    impl Add for Complex<i32> {
+        type Output = Complex<i32>;
+        fn add(self, rhs: Self) -> Self {
+            Complex {
+                re: self.re + rhs.re,
+                im: self.im + rhs.im,
+            }
+        }
     }
 }
 
-#[test]
-fn add_complex_to_real() {
-    assert_eq!(30f64 + Complex { re: 10.0f64, im: 20.0 },
-               Complex { re: 40.0, im: 20.0 });
-}
+mod somewhat_generic {
+    define_complex!();
 
-use std::ops::Neg;
+    use std::ops::Add;
 
-impl<T, O> Neg for Complex<T>
-    where T: Neg<Output=O>
-{
-    type Output = Complex<O>;
-    fn neg(self) -> Complex<O> {
-        Complex { re: -self.re, im: -self.im }
+    impl<T> Add for Complex<T>
+    where
+        T: Add<Output = T>,
+    {
+        type Output = Self;
+        fn add(self, rhs: Self) -> Self {
+            Complex {
+                re: self.re + rhs.re,
+                im: self.im + rhs.im,
+            }
+        }
     }
-}
 
-#[test]
-fn negate_complex() {
-    let z = Complex { re: 3, im: 4 };
-    assert_eq!(-z, Complex { re: -3, im: -4 });
+    use std::ops::Neg;
+
+    impl<T> Neg for Complex<T>
+    where
+        T: Neg<Output = T>,
+    {
+        type Output = Complex<T>;
+        fn neg(self) -> Complex<T> {
+            Complex {
+                re: -self.re,
+                im: -self.im,
+            }
+        }
+    }
 }
 
-use std::ops::AddAssign;
+mod very_generic {
+    define_complex!();
+
+    use std::ops::Add;
 
-impl<T> AddAssign for Complex<T>
-    where T: AddAssign<T>
-{
-    fn add_assign(&mut self, rhs: Complex<T>) {
-        self.re += rhs.re;
-        self.im += rhs.im;
+    impl<L, R> Add<Complex<R>> for Complex<L>
+    where
+        L: Add<R>,
+    {
+        type Output = Complex<L::Output>;
+        fn add(self, rhs: Complex<R>) -> Self::Output {
+            Complex {
+                re: self.re + rhs.re,
+                im: self.im + rhs.im,
+            }
+        }
     }
 }
 
-#[test]
-fn compound_assignment() {
-    let mut z = Complex { re: 5, im: 6 };
-    z += Complex { re: 7, im: 8 };
-    assert_eq!(z, Complex { re: 12, im: 14 });
+mod impl_compound {
+    define_complex!();
+
+    use std::ops::AddAssign;
 
-    let mut title = "Love".to_string();
-    title += ", Actually";
-    assert_eq!(title, "Love, Actually");
+    impl<T> AddAssign for Complex<T>
+    where
+        T: AddAssign<T>,
+    {
+        fn add_assign(&mut self, rhs: Complex<T>) {
+            self.re += rhs.re;
+            self.im += rhs.im;
+        }
+    }
 }
 
-impl<T: PartialEq> PartialEq for Complex<T> {
-    fn eq(&self, other: &Complex<T>) -> bool {
-        self.re == other.re && self.im == other.im
+mod derive_partialeq {
+    #[derive(Clone, Copy, Debug, PartialEq)]
+    struct Complex<T> {
+        re: T,
+        im: T,
     }
 }
 
-impl<T: Eq> Eq for Complex<T> { }
+mod derive_everything {
+    #[derive(Clone, Copy, Debug, Eq, PartialEq)]
+    struct Complex<T> {
+        /// Real portion of the complex number
+        re: T,
 
-#[test]
-fn comparison() {
-    let x = Complex { re: 5, im: 2 };
-    let y = Complex { re: 2, im: 5 };
-    assert_eq!(x * y, Complex { re: 0, im: 29 });
+        /// Imaginary portion of the complex number
+        im: T,
+    }
 }
 
-use std::fmt;
+/// Examples from Chapter 17, Strings and Text
+///
+/// These use a separate, non-generic `Complex` type, for simplicity.
+mod formatting {
+    #[test]
+    fn complex() {
+        #[derive(Copy, Clone, Debug)]
+        struct Complex { re: f64, im: f64 }
 
-// To make the formatting examples mesh with the rest of this file, I've adapted
-// them to work on the type `Complex<f64>`, where the book simply defines a new
-// non-generic `Complex` type. The only changes are adding `<f64>`, and changing
-// the field names.
+        let third = Complex { re: -0.5, im: f64::sqrt(0.75) };
+        println!("{:?}", third);
 
-#[cfg(skip)]
-impl fmt::Display for Complex<f64> {
-    fn fmt(&self, dest: &mut fmt::Formatter) -> fmt::Result {
-        let i_sign = if self.i < 0.0 { '-' } else { '+' };
-        write!(dest, "{} {} {}i", self.r, i_sign, f64::abs(self.i))
-    }
-}
+        use std::fmt;
 
-impl fmt::Display for Complex<f64> {
-    fn fmt(&self, dest: &mut fmt::Formatter) -> fmt::Result {
-        let (r, i) = (self.re, self.im);
-        if dest.alternate() {
-            let abs = f64::sqrt(r * r + i * i);
-            let angle = f64::atan2(i, r) / std::f64::consts::PI * 180.0;
-            write!(dest, "{} ∠ {}°", abs, angle)
-        } else {
-            let i_sign = if i < 0.0 { '-' } else { '+' };
-            write!(dest, "{} {} {}i", r, i_sign, f64::abs(i))
+        impl fmt::Display for Complex {
+            fn fmt(&self, dest: &mut fmt::Formatter) -> fmt::Result {
+                let im_sign = if self.im < 0.0 { '-' } else { '+' };
+                write!(dest, "{} {} {}i", self.re, im_sign, f64::abs(self.im))
+            }
         }
+
+        let one_twenty = Complex { re: -0.5, im: 0.866 };
+        assert_eq!(format!("{}", one_twenty),
+                   "-0.5 + 0.866i");
+
+        let two_forty = Complex { re: -0.5, im: -0.866 };
+        assert_eq!(format!("{}", two_forty),
+                   "-0.5 - 0.866i");
     }
-}
 
-#[test]
-fn custom_display_impl() {
-    let one_twenty = Complex { re: -0.5, im: 0.866 };
-    assert_eq!(format!("{}", one_twenty),
-               "-0.5 + 0.866i");
-
-    let two_forty = Complex { re: -0.5, im: -0.866 };
-    assert_eq!(format!("{}", two_forty),
-               "-0.5 - 0.866i");
-
-    let ninety = Complex { re: 0.0, im: 2.0 };
-    assert_eq!(format!("{}", ninety),
-               "0 + 2i");
-    assert_eq!(format!("{:#}", ninety),
-               "2 ∠ 90°");
+    #[test]
+    fn complex_fancy() {
+        #[derive(Copy, Clone, Debug)]
+        struct Complex { re: f64, im: f64 }
+
+        use std::fmt;
+
+        impl fmt::Display for Complex {
+            fn fmt(&self, dest: &mut fmt::Formatter) -> fmt::Result {
+                let (re, im) = (self.re, self.im);
+                if dest.alternate() {
+                    let abs = f64::sqrt(re * re + im * im);
+                    let angle = f64::atan2(im, re) / std::f64::consts::PI * 180.0;
+                    write!(dest, "{} ∠ {}°", abs, angle)
+                } else {
+                    let im_sign = if im < 0.0 { '-' } else { '+' };
+                    write!(dest, "{} {} {}i", re, im_sign, f64::abs(im))
+                }
+            }
+        }
+
+        let ninety = Complex { re: 0.0, im: 2.0 };
+        assert_eq!(format!("{}", ninety),
+                   "0 + 2i");
+        assert_eq!(format!("{:#}", ninety),
+                   "2 ∠ 90°");
+    }
 }