Math.hpp

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#pragma once
 
#include <algorithm>
#include <cmath>
 
#include "utils/Types.hpp"
 
#define APPROX_THRESHOLD 0.01

namespace ppforest2::math {
  template<typename A, typename B, typename T> inline bool is_approx(A a, B b, T threshold) {
    return fabs(a - b) < threshold;
  }

  template<typename A, typename B> inline bool is_approx(A a, B b) {
    return is_approx(a, b, APPROX_THRESHOLD);
  }

  template<typename A, typename B> inline bool is_module_approx(A a, B b) {
    return is_approx(fabs(a), fabs(b));
  }

  template<typename T> bool collinear(types::Vector<T> const& a, types::Vector<T> const& b) {
    return is_module_approx(a.dot(b) / (a.norm() * b.norm()), 1.0);
  }

  inline int proportion_to_count(float p, unsigned int total) {
    float const value = static_cast<float>(total) * p;
    float const lower = std::floor(value);
    float const fract = value - lower;
 
    int count = static_cast<int>(lower);
    // Round up past the halfway point, or exactly at it when the floor is odd
    // (ties to even). Mirrors std::nearbyint's default-mode result without
    // reading the floating-point environment.
    if (fract > 0.5F || (fract == 0.5F && count % 2 != 0)) {
      count += 1;
    }
    return std::max(1, count);
  }
}