Flesh out Fraction class

This is to support fraction based manadatory sidestake allocations.
jamescowens · Jan 20, 2024 · f3707bb · f3707bb
1 parent 878e4ff
commit f3707bb
Showing 1 changed file with 274 additions and 9 deletions.
diff --git a/src/util.h b/src/util.h
@@ -11,6 +11,7 @@
 #include "hash.h"
 
 #include <memory>
+#include <numeric>
 #include <utility>
 #include <map>
 #include <vector>
@@ -160,13 +161,25 @@ inline int64_t abs64(int64_t n)
     return (n >= 0 ? n : -n);
 }
 
-// Small class to represent fractions. We could do more sophisticated things like reduction using GCD, and overloaded
-// multiplication, but we don't need it, because this is used in very limited places, and we actually in many of the
-// algorithms where this needs to be used need to carefully control the order of multiplication and division using the
-// numerator and denominator.
+//!
+//! \brief Class to represent fractions and common operations with built in simplification. This supports integer operations
+//! for consensus critical code where floating point would cause problems across different architectures and/or compiler
+//! implementations
+//!
 class Fraction {
 public:
-    Fraction() {}
+    Fraction()
+        : m_numerator(0)
+        , m_denominator(1)
+    {}
+
+    Fraction(const Fraction& f)
+        : Fraction(f.GetNumerator(), f.GetDenominator())
+    {}
+
+    Fraction(const Fraction& f, const bool& simplify)
+        : Fraction(f.GetNumerator(), f.GetDenominator(), simplify)
+    {}
 
     Fraction(const int64_t& numerator,
              const int64_t& denominator)
@@ -178,9 +191,44 @@ class Fraction {
         }
     }
 
-    bool isNonZero()
+    Fraction(const int64_t& numerator,
+             const int64_t& denominator,
+             const bool& simplify)
+        : Fraction(numerator, denominator)
+    {
+        if (simplify) {
+            Simplify();
+        }
+    }
+
+    Fraction(const int64_t& numerator)
+        : Fraction(numerator, 1)
+    {}
+
+    bool isZero() const
+    {
+        // The denominator cannot be zero by construction rules.
+        return m_numerator == 0;
+    }
+
+    bool isNonZero() const
+    {
+        return !isZero();
+    }
+
+    bool isPositive() const
+    {
+        return (m_denominator > 0 && m_numerator > 0) || (m_denominator < 0 && m_numerator < 0);
+    }
+
+    bool isNonNegative() const
     {
-        return m_denominator != 0 && m_numerator != 0;
+        return isPositive() || isZero();
+    }
+
+    bool isNegative() const
+    {
+        return !isNonNegative();
     }
 
     constexpr int64_t GetNumerator() const
@@ -193,9 +241,226 @@ class Fraction {
         return m_denominator;
     }
 
+    bool IsSimplified() const
+    {
+        return std::gcd(m_numerator, m_denominator) == (int64_t) 1;
+    }
+
+    void Simplify()
+    {
+        // Nice that we are at C++17! :)
+        int64_t gcd = std::gcd(m_numerator, m_denominator);
+
+        // If both numerator and denominator are negative,
+        // change the sign of gcd to flip both to positive.
+        if (m_numerator < 0 && m_denominator < 0) {
+            gcd = -gcd;
+        }
+
+        m_numerator = m_numerator / gcd;
+        m_denominator = m_denominator / gcd;
+
+    }
+
+    Fraction operator=(const Fraction& rhs)
+    {
+        m_numerator = rhs.GetNumerator();
+        m_denominator = rhs.GetDenominator();
+
+        return *this;
+    }
+
+    Fraction operator+(const Fraction& rhs) const
+    {
+        Fraction slhs(*this, true);
+        Fraction srhs(rhs, true);
+
+        return Fraction(slhs.GetNumerator() * srhs.GetDenominator() + slhs.GetDenominator() * srhs.GetNumerator(),
+                        slhs.GetDenominator() * srhs.GetDenominator(), true);
+    }
+
+    Fraction operator+(const int64_t& rhs) const
+    {
+        Fraction slhs(*this, true);
+
+        return Fraction(slhs.GetNumerator() + rhs * slhs.GetDenominator(), slhs.GetDenominator(), true);
+    }
+
+    Fraction operator-(const Fraction& rhs) const
+    {
+        return (*this + Fraction(-rhs.GetNumerator(), rhs.GetDenominator()));
+    }
+
+    Fraction operator-(const int64_t& rhs) const
+    {
+        return (*this + -rhs);
+    }
+
+    Fraction operator*(const Fraction& rhs) const
+    {
+        Fraction slhs(*this, true);
+        Fraction srhs(rhs, true);
+
+        return Fraction(slhs.GetNumerator() * srhs.GetNumerator(), slhs.GetDenominator() * srhs.GetDenominator(), true);
+    }
+
+    Fraction operator*(const int64_t& rhs) const
+    {
+        Fraction slhs(*this, true);
+
+        return Fraction(slhs.GetNumerator() * rhs, slhs.GetDenominator(), true);
+    }
+
+    Fraction operator/(const Fraction& rhs) const
+    {
+        return (*this * Fraction(rhs.GetDenominator(), rhs.GetNumerator()));
+    }
+
+    Fraction operator/(const int64_t& rhs) const
+    {
+        Fraction slhs(*this, true);
+
+        return Fraction(slhs.GetNumerator(), slhs.GetDenominator() * rhs, true);
+    }
+
+    Fraction operator+=(const Fraction& rhs)
+    {
+        Simplify();
+
+        *this = *this + rhs;
+
+        return *this;
+    }
+
+    Fraction operator+=(const int64_t& rhs)
+    {
+        Simplify();
+
+        *this = *this + rhs;
+
+        return *this;
+    }
+
+    Fraction operator-=(const Fraction& rhs)
+    {
+        Simplify();
+
+        *this = *this - rhs;
+
+        return *this;
+    }
+
+    Fraction operator-=(const int64_t& rhs)
+    {
+        Simplify();
+
+        *this = *this - rhs;
+
+        return *this;
+    }
+
+    Fraction operator*=(const Fraction& rhs)
+    {
+        Simplify();
+
+        *this = *this * rhs;
+
+        return *this;
+    }
+
+    Fraction operator*=(const int64_t& rhs)
+    {
+        Simplify();
+
+        *this = *this * rhs;
+
+        return *this;
+    }
+
+    Fraction operator/=(const Fraction& rhs)
+    {
+        Simplify();
+
+        *this = *this / rhs;
+
+        return *this;
+    }
+
+    Fraction operator/=(const int64_t& rhs)
+    {
+        Simplify();
+
+        *this = *this / rhs;
+
+        return *this;
+    }
+
+    bool operator==(const Fraction& rhs) const
+    {
+        Fraction slhs(*this, true);
+        Fraction srhs(rhs, true);
+
+        return (slhs.GetNumerator() == srhs.GetNumerator() && slhs.GetDenominator() == slhs.GetDenominator());
+    }
+
+    bool operator!=(const Fraction& rhs) const
+    {
+        return !(*this == rhs);
+    }
+
+    bool operator<=(const Fraction& rhs) const
+    {
+        return (rhs - *this).isNonNegative();
+    }
+
+    bool operator>=(const Fraction& rhs) const
+    {
+        return (*this - rhs).isNonNegative();
+    }
+
+    bool operator<(const Fraction& rhs) const
+    {
+        return (rhs - *this).isPositive();
+    }
+
+    bool operator>(const Fraction& rhs) const
+    {
+        return (*this - rhs).isPositive();
+    }
+
+    bool operator==(const int64_t& rhs) const
+    {
+        return (*this == Fraction(rhs));
+    }
+
+    bool operator!=(const int64_t& rhs) const
+    {
+        return !(*this == rhs);
+    }
+
+    bool operator<=(const int64_t& rhs) const
+    {
+        return *this <= Fraction(rhs);
+    }
+
+    bool operator>=(const int64_t& rhs) const
+    {
+        return *this >= Fraction(rhs);
+    }
+
+    bool operator<(const int64_t& rhs) const
+    {
+        return *this < Fraction(rhs);
+    }
+
+    bool operator>(const int64_t& rhs) const
+    {
+        return *this > Fraction(rhs);
+    }
+
 private:
-    int64_t m_numerator = 0;
-    int64_t m_denominator = 1;
+    int64_t m_numerator;
+    int64_t m_denominator;
 };
 
 inline std::string leftTrim(std::string src, char chr)