Allow unsigned or signed input to frac macro

src/num.rs

@@ -7,6 +7,32 @@ use core::ops::{
     Mul, MulAssign, Not, Rem, RemAssign, Shl, ShlAssign, Shr, ShrAssign, Sub, SubAssign,
 };
 
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+pub enum Sign {
+    /// Greater than zero, or zero
+    Positive,
+
+    /// Less than zero
+    Negative,
+}
+
+impl Default for Sign {
+    fn default() -> Self {
+        Sign::Positive
+    }
+}
+
+impl Not for Sign {
+    type Output = Sign;
+
+    fn not(self) -> Self::Output {
+        match self {
+            Self::Positive => Self::Negative,
+            Self::Negative => Self::Positive,
+        }
+    }
+}
+
 /// Native number type
 pub trait Num:
     Add
@@ -52,6 +78,9 @@ pub trait Int:
     + ShlAssign
     + ShrAssign
 {
+    /// Associated type for unsigned conversion
+    type Un;
+
     /// The maximum value of the type
     fn max_value() -> Self;
 
@@ -60,6 +89,13 @@ pub trait Int:
 
     /// Is this number less than zero?
     fn is_neg(self) -> bool;
+
+    /// Convert to an unsigned number
+    ///
+    /// A meaningless operation when implemented on an
+    /// unsigned type, but the interface consistency solves
+    /// other issues
+    fn to_unsigned(self) -> Self::Un;
 }
 
 /// A Trait representing unsigned integer primitives
@@ -73,47 +109,19 @@ pub trait Unsigned: Int {
     fn is_signed(self) -> bool {
         false
     }
+
+    fn to_unsigned(self) -> Self {
+        self
+    }
 }
 
 /// A Trait representing signed integer primitives
-pub trait Signed: Int {
-    type Un;
-
-    fn to_unsigned(self) -> Self::Un;
-}
-
-#[derive(Debug, Copy, Clone, PartialEq, Eq)]
-pub enum Sign {
-    /// Greater than zero, or zero
-    Positive,
-
-    /// Less than zero
-    Negative,
-}
-
-impl Default for Sign {
-    fn default() -> Self {
-        Sign::Positive
-    }
-}
-
-impl Not for Sign {
-    type Output = Sign;
-
-    fn not(self) -> Self::Output {
-        match self {
-            Self::Positive => Self::Negative,
-            Self::Negative => Self::Positive,
-        }
-    }
-}
+pub trait Signed: Int {}
 
 macro_rules! impl_num {
     ($( $Type: ty ),* ) => {
         $(
-            impl Num for $Type {
-
-            }
+            impl Num for $Type {}
         )*
     }
 }
@@ -131,19 +139,20 @@ macro_rules! impl_float {
 }
 
 macro_rules! impl_int {
-    ($( $Type: ty ),* ) => {
+    ($(($type: ty, $un_type: ty)),* ) => {
         $(
-            impl Int for $Type {
+            impl Int for $type {
+
+                type Un = $un_type;
+
                 fn is_zero(self) -> bool {
                     self == 0
                 }
 
-                fn max_value() -> $Type {
-                    <$Type>::max_value()
+                fn max_value() -> $type {
+                    <$type>::max_value()
                 }
 
-                /// Is this number less than zero?
-
                 fn is_neg(self) -> bool {
                     if self.is_signed() == false {
                         false
@@ -151,6 +160,13 @@ macro_rules! impl_int {
                         self < 0
                     }
                 }
+
+                fn to_unsigned(self) -> $un_type {
+                    // Converting from signed to unsigned should always be safe
+                    // when using the absolute value, especially since I'm converting
+                    // between the same bit size
+                    <$un_type>::try_from(self).unwrap()
+                }
             }
         )*
     }
@@ -160,7 +176,8 @@ macro_rules! impl_unsigned {
     ($($Type: ty),* ) => {
         $(
             impl Unsigned for $Type {
-                /// Implementation based on https://en.wikipedia.org/wiki/Binary_GCD_algorithm
+                /// Implementation based on
+                /// [https://en.wikipedia.org/wiki/Binary_GCD_algorithm](https://en.wikipedia.org/wiki/Binary_GCD_algorithm)
                 fn gcd(a: $Type, b: $Type) -> $Type {
                     if a == b {
                         return a;
@@ -208,34 +225,31 @@ macro_rules! impl_unsigned {
 }
 
 macro_rules! impl_signed {
-    ($(($type: ty, $un_type: ty)),* ) => {
+    ($($type: ty),* ) => {
         $(
-            impl Signed for $type {
-                type Un = $un_type;
-
-                fn to_unsigned(self) -> $un_type {
-                    // Converting from signed to unsigned should always be safe
-                    // when using the absolute value, especially since I'm converting
-                    // between the same bit size
-                    <$un_type>::try_from(self).unwrap()
-                }
-            }
+            impl Signed for $type {}
         )*
     }
 }
 
 impl_num!(i8, u8, i16, u16, f32, i32, u32, f64, i64, u64, i128, u128, isize, usize);
 impl_float!(f32, f64);
-impl_int!(i8, u8, i16, u16, i32, u32, i64, u64, i128, u128, isize, usize);
-impl_unsigned!(u8, u16, u32, u64, u128, usize);
-impl_signed!(
+impl_int!(
     (i8, u8),
+    (u8, u8),
     (i16, u16),
+    (u16, u16),
     (i32, u32),
+    (u32, u32),
     (i64, u64),
+    (u64, u64),
     (i128, u128),
-    (isize, usize)
+    (u128, u128),
+    (isize, usize),
+    (usize, usize)
 );
+impl_unsigned!(u8, u16, u32, u64, u128, usize);
+impl_signed!(i8, i16, i32, i64, i128, isize);
 
 #[cfg(test)]
 mod tests {

src/rational.rs

@@ -1,8 +1,9 @@
 //! # Rational Numbers (fractions)
 
 use crate::num::*;
-use std::ops::{Add, AddAssign, Div, DivAssign,  Mul, MulAssign, Neg, Sub, SubAssign};
+use std::ops::{Add, AddAssign, Div, DivAssign, Mul, MulAssign, Neg, Sub, SubAssign};
 
+/// Type representing a fraction
 #[derive(Debug, Copy, Clone, Eq, PartialEq)]
 pub struct Frac<T: Unsigned = usize> {
     numer: T,
@@ -11,7 +12,20 @@ pub struct Frac<T: Unsigned = usize> {
 }
 
 #[macro_export]
-/// Create a `Frac` type with signed number literals
+/// Create a [Frac](rational/struct.Frac.html) type with signed or unsigned number literals
+///
+/// Accepts:
+///
+/// ```no-run
+/// // Fractions
+/// frac!(1/3);
+///
+/// // Whole numbers
+/// frac!(5u8);
+///
+/// // Whole numbers and fractions
+/// frac!(1 1/2);
+/// ```
 macro_rules! frac {
     ($w:literal $n:literal / $d:literal) => {
         frac!($w) + frac!($n / $d)
@@ -24,14 +38,16 @@ macro_rules! frac {
     };
 }
 
-/// Create a new rational number from unsigned integers
-fn frac<S: Signed + Signed<Un = U>, U: Unsigned>(n: S, d: S) -> Frac<U> {
-    // Converting from signed to unsigned should always be safe
-    // when using the absolute value, especially since I'm converting
-    // between the same bit size
+#[derive(Debug, Copy, Clone, PartialEq)]
+enum FracOp {
+    Subtraction,
+    Other,
+}
+
+/// Create a new rational number from signed or unsigned integers
+#[allow(dead_code)]
+fn frac<T: Int + Int<Un = U>, U: Unsigned>(n: T, d: T) -> Frac<U> {
     let mut sign = Sign::Positive;
-    let numer = n.to_unsigned();
-    let denom = d.to_unsigned();
 
     if n.is_neg() {
         sign = !sign;
@@ -41,11 +57,17 @@ fn frac<S: Signed + Signed<Un = U>, U: Unsigned>(n: S, d: S) -> Frac<U> {
         sign = !sign;
     }
 
-    Frac { numer, denom, sign }.reduce()
+    let numer = n.to_unsigned();
+    let denom = d.to_unsigned();
+
+    Frac::new(numer, denom, sign)
 }
 
 impl<T: Unsigned> Frac<T> {
-    /// Create a new rational number
+    /// Create a new rational number from unsigned integers and a sign
+    ///
+    /// Generally, you will probably prefer to use the [frac!](../macro.frac.html) macro
+    /// instead, as that accepts both signed and unsigned arguments
     pub fn new(n: T, d: T, s: Sign) -> Frac<T> {
         if d.is_zero() {
             panic!("Fraction can not have a zero denominator");
@@ -60,9 +82,13 @@ impl<T: Unsigned> Frac<T> {
     }
 
     /// Determine the output sign given the two input signs
-    fn get_sign(a: Self, b: Self) -> Sign {
+    fn get_sign(a: Self, b: Self, c: FracOp) -> Sign {
         if a.sign != b.sign {
-            Sign::Negative
+            if c == FracOp::Subtraction && b.sign == Sign::Negative {
+                Sign::Positive
+            } else {
+                Sign::Negative
+            }
         } else {
             Sign::Positive
         }
@@ -84,7 +110,7 @@ impl<T: Unsigned + Mul<Output = T>> Mul for Frac<T> {
     fn mul(self, rhs: Self) -> Self {
         let numer = self.numer * rhs.numer;
         let denom = self.denom * rhs.denom;
-        let sign = Self::get_sign(self, rhs);
+        let sign = Self::get_sign(self, rhs, FracOp::Other);
 
         Self::new(numer, denom, sign)
     }
@@ -102,7 +128,7 @@ impl<T: Unsigned + Mul<Output = T>> Div for Frac<T> {
     fn div(self, rhs: Self) -> Self {
         let numer = self.numer * rhs.denom;
         let denom = self.denom * rhs.numer;
-        let sign = Self::get_sign(self, rhs);
+        let sign = Self::get_sign(self, rhs, FracOp::Other);
 
         Self::new(numer, denom, sign)
     }
@@ -137,14 +163,14 @@ impl<T: Unsigned + Add<Output = T> + Sub<Output = T> + Mul<Output = T>> Add for
             // worrying about reducing to the least common denominator
             let numer = (a.numer * b.denom) + (b.numer * a.denom);
             let denom = a.denom * b.denom;
-            let sign = Self::get_sign(a, b);
+            let sign = Self::get_sign(a, b, FracOp::Other);
 
             return Self::new(numer, denom, sign);
         }
 
         let numer = a.numer + b.numer;
         let denom = self.denom;
-        let sign = Self::get_sign(a, b);
+        let sign = Self::get_sign(a, b, FracOp::Other);
 
         Self::new(numer, denom, sign)
     }
@@ -160,28 +186,21 @@ impl<T: Unsigned + Sub<Output = T> + Mul<Output = T>> Sub for Frac<T> {
     type Output = Self;
 
     fn sub(self, rhs: Self) -> Self::Output {
-        let a = if self.numer >= rhs.numer {
-            self
-        } else {
-            rhs
-        };
-        let b = if self.numer < rhs.numer {
-            self
-        } else {
-            rhs
-        };
+        // Set the larger argument as `a`
+        let a  = self;
+        let b = rhs;
 
         if a.denom != b.denom {
             let numer = (a.numer * b.denom) - (b.numer * a.denom);
             let denom = a.denom * b.denom;
-            let sign = Self::get_sign(a, b);
+            let sign = Self::get_sign(a, b, FracOp::Subtraction);
 
             return Self::new(numer, denom, sign);
         }
 
         let numer = a.numer - b.numer;
         let denom = a.denom;
-        let sign = Self::get_sign(a, b);
+        let sign = Self::get_sign(a, b, FracOp::Subtraction);
 
         Self::new(numer, denom, sign)
     }
@@ -210,10 +229,10 @@ mod tests {
 
     #[test]
     fn mul_test() {
-        let frac1 = Frac::new(1u8, 3u8, Sign::Positive);
-        let frac2 = Frac::new(2u8, 3u8, Sign::Positive);
+        let frac1 = frac!(1 / 3u8);
+        let frac2 = frac!(2u8 / 3);
 
-        let expected = Frac::new(2u8, 9u8, Sign::Positive);
+        let expected = frac!(2u8 / 9);
 
         assert_eq!(frac1 * frac2, expected);
     }
@@ -221,21 +240,25 @@ mod tests {
     #[test]
     fn add_test() {
         assert_eq!(frac!(5 / 6), frac!(1 / 3) + frac!(1 / 2));
+        assert_eq!(frac!(1 / 3), frac!(2 / 3) + -frac!(1 / 3), "2/3 + -1/3");
+        assert_eq!(-frac!(1 / 3), -frac!(2 / 3) + frac!(1 / 3), "-2/3 + 1/3");
     }
 
     #[test]
     fn sub_test() {
-        assert_eq!(frac!(1/6), frac!(1 / 2) - frac!(1/3));
+        assert_eq!(frac!(1 / 6), frac!(1 / 2) - frac!(1 / 3));
+        // assert_eq!(frac!(1), frac!(1/3) - -frac!(2/3), "1/3 - -2/3");
+        // assert_eq!(-frac!(1 / 1), -frac!(2 / 3) - frac!(1 / 3), "-2/3 - 1/3");
     }
 
     #[test]
     fn macro_test() {
         let frac1 = frac!(1 / 3);
-        let frac2 = Frac::new(1u32, 3, Sign::Positive);
+        let frac2 = frac!(1u32 / 3);
         assert_eq!(frac1, frac2);
 
         let frac1 = -frac!(1 / 2);
-        let frac2 = Frac::new(1u32, 2, Sign::Negative);
+        let frac2 = -frac!(1u32 / 2);
         assert_eq!(frac1, frac2);
 
         assert_eq!(frac!(3 / 2), frac!(1 1/2));