cpp-mathematic-limit/include/math/limit.h

//
//  limit.h
//  utilities
//
//  Created by Sam Jaffe on 10/22/13.
//  Copyright (c) 2013 Sam Jaffe. All rights reserved.
//

#pragma once

#include <type_traits>

#include <math/clamp.h>

namespace math {

struct {
} assert_bounds;
using AssertBounds = decltype(assert_bounds);

template <typename T, auto MINIMUM_VALUE, auto MAXIMUM_VALUE> class Bound final {
public:
  static_assert(MINIMUM_VALUE <= MAXIMUM_VALUE,
                "The minimum value must be less than or equal to the maximum");

  using value_type = T;
  using underlying_type = value_type const &;
  using bound_type =
      std::common_type_t<decltype(MAXIMUM_VALUE), decltype(MINIMUM_VALUE)>;

  static constexpr const bound_type min = MINIMUM_VALUE;
  static constexpr const bound_type max = MAXIMUM_VALUE;

private:
  value_type value_;

public:
  constexpr Bound() : value_(clamp(value_type(), min, max)) {}
  constexpr Bound(value_type const & val) noexcept
      : value_(clamp(val, min, max)) {}

  Bound(AssertBounds, value_type val) : value_(assert_in_bounds(val, min, max)) {}

  explicit operator value_type const &() const { return value_; }
  value_type const &operator*() const { return value_; }
  value_type const *operator->() const { return &value_; }

  auto operator<=>(Bound const &other) const noexcept = default;

  template <typename F> void mutate(F &&func) {
    std::forward<F>(func)(value_);
    *this = Bound(value_);
  }
  
  Bound & operator-=(value_type by) { return *this = Bound(value_ - by); }
  Bound & operator+=(value_type by) { return *this = Bound(value_ + by); }
  Bound operator+(value_type by) const { return Bound{*this} += by; }
  Bound operator-(value_type by) const { return Bound{*this} -= by; }
  Bound & operator--() { return *this -= 1; }
  Bound & operator++() { return *this += 1; }

  Bound operator--(int) {
    Bound tmp = *this;
    operator--();
    return tmp;
  }

  Bound operator++(int) {
    Bound tmp = *this;
    operator++();
    return tmp;
  }
};

template <typename T, auto MINMAX> using SymBound = Bound<T, -MINMAX, +MINMAX>;
template <typename T, auto VAL>
using UniBound =
    std::conditional_t<0 <= VAL, Bound<T, 0, VAL>, Bound<T, VAL, 0>>;

template <typename T, auto MIN, auto MAX, typename R>
auto operator+(Bound<T, MIN, MAX> const &lhs, R const &rhs) {
  return *lhs + rhs;
}

template <typename L, auto L_MIN, auto L_MAX, typename R, auto R_MIN, auto R_MAX>
auto operator+(Bound<L, L_MIN, L_MAX> const &lhs, Bound<R, R_MIN, R_MAX> const &rhs) {
  return *lhs + *rhs;
}

template <typename T, auto MIN, auto MAX, typename R>
auto operator-(Bound<T, MIN, MAX> const &lhs, R const &rhs) {
  return *lhs - rhs;
}

template <typename L, auto L_MIN, auto L_MAX, typename R, auto R_MIN, auto R_MAX>
auto operator-(Bound<L, L_MIN, L_MAX> const &lhs, Bound<R, R_MIN, R_MAX> const &rhs) {
  return *lhs - *rhs;
}

template <typename T, auto MIN, auto MAX, typename R>
auto operator*(Bound<T, MIN, MAX> const &lhs, R const &rhs) {
  return *lhs * rhs;
}

template <typename L, auto L_MIN, auto L_MAX, typename R, auto R_MIN, auto R_MAX>
auto operator*(Bound<L, L_MIN, L_MAX> const &lhs, Bound<R, R_MIN, R_MAX> const &rhs) {
  return *lhs * *rhs;
}

template <typename T, auto MIN, auto MAX, typename R>
auto operator/(Bound<T, MIN, MAX> const &lhs, R const &rhs) {
  return *lhs / rhs;
}

template <typename L, auto L_MIN, auto L_MAX, typename R, auto R_MIN, auto R_MAX>
auto operator/(Bound<L, L_MIN, L_MAX> const &lhs, Bound<R, R_MIN, R_MAX> const &rhs) {
  return *lhs / *rhs;
}

template <typename T, auto MIN, auto MAX, typename R>
auto min(Bound<T, MIN, MAX> const &lhs, R const &rhs) {
  using std::min;
  return min(*lhs, rhs);
}

template <typename T, auto MIN, auto MAX, typename R>
auto max(Bound<T, MIN, MAX> const &lhs, R const &rhs) {
  using std::max;
  return max(*lhs, rhs);
}
}