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diff --git a/source/blender/blenlib/BLI_mpq2.hh b/source/blender/blenlib/BLI_mpq2.hh
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+/*
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ */
+
+#pragma once
+
+/** \file
+ * \ingroup bli
+ */
+
+#ifdef WITH_GMP
+
+#  include "BLI_math_mpq.hh"
+#  include "BLI_mpq3.hh"
+
+namespace blender {
+
+struct mpq2 {
+  mpq_class x, y;
+
+  mpq2() = default;
+
+  mpq2(const mpq_class *ptr) : x{ptr[0]}, y{ptr[1]}
+  {
+  }
+
+  mpq2(mpq_class x, mpq_class y) : x(x), y(y)
+  {
+  }
+
+  mpq2(const mpq2 &other) : x(other.x), y(other.y)
+  {
+  }
+
+  mpq2(mpq2 &&other) noexcept : x(std::move(other.x)), y(std::move(other.y))
+  {
+  }
+
+  ~mpq2() = default;
+
+  mpq2 &operator=(const mpq2 &other)
+  {
+    if (this != &other) {
+      x = other.x;
+      y = other.y;
+    }
+    return *this;
+  }
+
+  mpq2 &operator=(mpq2 &&other) noexcept
+  {
+    x = std::move(other.x);
+    y = std::move(other.y);
+    return *this;
+  }
+
+  mpq2(const mpq3 &other) : x(other.x), y(other.y)
+  {
+  }
+
+  operator mpq_class *()
+  {
+    return &x;
+  }
+
+  operator const mpq_class *() const
+  {
+    return &x;
+  }
+
+  /**
+   * Cannot do this exactly in rational arithmetic!
+   * Approximate by going in and out of doubles.
+   */
+  mpq_class length() const
+  {
+    mpq_class lsquared = dot(*this, *this);
+    return mpq_class(sqrt(lsquared.get_d()));
+  }
+
+  friend mpq2 operator+(const mpq2 &a, const mpq2 &b)
+  {
+    return {a.x + b.x, a.y + b.y};
+  }
+
+  friend mpq2 operator-(const mpq2 &a, const mpq2 &b)
+  {
+    return {a.x - b.x, a.y - b.y};
+  }
+
+  friend mpq2 operator*(const mpq2 &a, mpq_class b)
+  {
+    return {a.x * b, a.y * b};
+  }
+
+  friend mpq2 operator/(const mpq2 &a, mpq_class b)
+  {
+    BLI_assert(b != 0);
+    return {a.x / b, a.y / b};
+  }
+
+  friend mpq2 operator*(mpq_class a, const mpq2 &b)
+  {
+    return b * a;
+  }
+
+  friend bool operator==(const mpq2 &a, const mpq2 &b)
+  {
+    return a.x == b.x && a.y == b.y;
+  }
+
+  friend bool operator!=(const mpq2 &a, const mpq2 &b)
+  {
+    return a.x != b.x || a.y != b.y;
+  }
+
+  friend std::ostream &operator<<(std::ostream &stream, const mpq2 &v)
+  {
+    stream << "(" << v.x << ", " << v.y << ")";
+    return stream;
+  }
+
+  static mpq_class dot(const mpq2 &a, const mpq2 &b)
+  {
+    return a.x * b.x + a.y * b.y;
+  }
+
+  static mpq2 interpolate(const mpq2 &a, const mpq2 &b, mpq_class t)
+  {
+    return a * (1 - t) + b * t;
+  }
+
+  static mpq2 abs(const mpq2 &a)
+  {
+    mpq_class abs_x = (a.x >= 0) ? a.x : -a.x;
+    mpq_class abs_y = (a.y >= 0) ? a.y : -a.y;
+    return mpq2(abs_x, abs_y);
+  }
+
+  static mpq_class distance(const mpq2 &a, const mpq2 &b)
+  {
+    return (a - b).length();
+  }
+
+  static mpq_class distance_squared(const mpq2 &a, const mpq2 &b)
+  {
+    return dot(a, b);
+  }
+
+  struct isect_result {
+    enum {
+      LINE_LINE_COLINEAR = -1,
+      LINE_LINE_NONE = 0,
+      LINE_LINE_EXACT = 1,
+      LINE_LINE_CROSS = 2,
+    } kind;
+    mpq_class lambda;
+    mpq_class mu;
+  };
+
+  static isect_result isect_seg_seg(const mpq2 &v1,
+                                    const mpq2 &v2,
+                                    const mpq2 &v3,
+                                    const mpq2 &v4);
+
+  /** There is a sensible use for hashing on exact arithmetic types. */
+  uint64_t hash() const;
+};
+
+}  // namespace blender
+
+#endif /* WITH_GMP */