Create lerp

Author: jurihock

src/Robocode/Header.h

@@ -2,7 +2,6 @@
 
 #include <algorithm>
 #include <array>
-#include <cassert>
 #include <cmath>
 #include <complex>
 #include <cstdint>
@@ -12,11 +11,13 @@
 #include <memory>
 #include <numbers>
 #include <numeric>
+#include <optional>
 #include <span>
 #include <stdexcept>
 #include <string>
 #include <utility>
 #include <vector>
 
 #include <Robocode/Assert.h>
+#include <Robocode/Lerp.h>
 #include <Robocode/Math.h>

src/Robocode/Lerp.cpp

@@ -0,0 +1,92 @@
+#include <Robocode/Lerp.h>
+
+Lerp::Lerp(const double v, const std::span<const double> x, const std::optional<double> z)
+{
+  if (x.empty())
+  {
+    throw std::invalid_argument("Vector x must be non-empty!");
+  }
+
+  config.s = x.size();
+  config.z = z;
+
+  if (v <= x.front())
+  {
+    config.u = -1;
+    return;
+  }
+
+  if (v >= x.back())
+  {
+    config.u = +1;
+    return;
+  }
+
+  auto b = std::lower_bound(x.begin(), x.end(), v);
+
+  if (b == x.begin())
+  {
+    config.u = -1;
+    return;
+  }
+
+  if (b == x.end())
+  {
+    config.u = +1;
+    return;
+  }
+
+  ptrdiff_t d = std::distance(x.begin(), b);
+  ptrdiff_t i = d - 1;
+  ptrdiff_t j = i + 1;
+
+  double x0 = x[i];
+  double x1 = x[j];
+  double t = (v - x0) / (x1 - x0);
+
+  config.i = i;
+  config.j = j;
+  config.t = t;
+}
+
+Lerp::Lerp(const Lerp& other) :
+  config(other.config)
+{
+}
+
+Lerp& Lerp::operator=(const Lerp& other)
+{
+  if (this != &other)
+  {
+    config = other.config;
+  }
+
+  return *this;
+}
+
+double Lerp::operator()(const std::span<const double> y) const
+{
+  const auto& [i, j, s, t, u, z] = config;
+
+  if (y.size() != s)
+  {
+    throw std::invalid_argument("Vectors x and y must be the same size!");
+  }
+
+  if (u < 0)
+  {
+    return z.value_or(y.front());
+  }
+  else if (u > 0)
+  {
+    return z.value_or(y.back());
+  }
+  else
+  {
+    double y0 = y[i];
+    double y1 = y[j];
+
+    // y0 + t * (y1 - y0)
+    return std::lerp(y0, y1, t);
+  }
+}

src/Robocode/Lerp.h

@@ -0,0 +1,34 @@
+#pragma once
+
+#include <algorithm>
+#include <cmath>
+#include <cstdint>
+#include <iterator>
+#include <optional>
+#include <span>
+
+class Lerp final
+{
+
+public:
+
+  Lerp(){};
+  Lerp(const double v, const std::span<const double> x, const std::optional<double> z = std::nullopt);
+  Lerp(const Lerp& other);
+  Lerp& operator=(const Lerp& other);
+
+  double operator()(const std::span<const double> y) const;
+
+private:
+
+  struct
+  {
+    ptrdiff_t i, j;
+    size_t s;
+    double t;
+    int u;
+    std::optional<double> z;
+  }
+  config;
+
+};