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+// MIT License
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+
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+// Copyright (c) 2019 Erin Catto
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+
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+// Permission is hereby granted, free of charge, to any person obtaining a copy
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+// of this software and associated documentation files (the "Software"), to deal
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+// in the Software without restriction, including without limitation the rights
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+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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+// copies of the Software, and to permit persons to whom the Software is
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+// furnished to do so, subject to the following conditions:
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+
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+// The above copyright notice and this permission notice shall be included in all
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+// copies or substantial portions of the Software.
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+
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+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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+// SOFTWARE.
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+
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+#ifndef B2_MATH_H
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+#define B2_MATH_H
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+
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+#include <math.h>
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+
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+/// This function is used to ensure that a floating point number is not a NaN or infinity.
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+inline bool b2IsValid(float x)
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+{
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+ return isfinite(x);
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+}
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+
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+#define b2Sqrt(x) sqrtf(x)
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+#define b2Atan2(y, x) atan2f(y, x)
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+
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+/// A 2D column vector.
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+struct b2Vec2
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+{
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+ /// Default constructor does nothing (for performance).
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+ b2Vec2() {}
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+
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+ /// Construct using coordinates.
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+ b2Vec2(float xIn, float yIn) : x(xIn), y(yIn) {}
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+
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+ /// Set this vector to all zeros.
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+ void SetZero() { x = 0.0f; y = 0.0f; }
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+
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+ /// Set this vector to some specified coordinates.
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+ void Set(float x_, float y_) { x = x_; y = y_; }
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+
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+ /// Negate this vector.
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+ b2Vec2 operator -() const { b2Vec2 v; v.Set(-x, -y); return v; }
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+
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+ /// Read from and indexed element.
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+ float operator () (int i) const
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+ {
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+ return (&x)[i];
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+ }
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+
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+ /// Write to an indexed element.
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+ float& operator () (int i)
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+ {
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+ return (&x)[i];
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+ }
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+
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+ /// Add a vector to this vector.
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+ void operator += (const b2Vec2& v)
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+ {
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+ x += v.x; y += v.y;
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+ }
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+
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+ /// Subtract a vector from this vector.
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+ void operator -= (const b2Vec2& v)
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+ {
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+ x -= v.x; y -= v.y;
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+ }
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+
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+ /// Multiply this vector by a scalar.
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+ void operator *= (float a)
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+ {
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+ x *= a; y *= a;
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+ }
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+
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+ /// Get the length of this vector (the norm).
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+ float Length() const
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+ {
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+ return b2Sqrt(x * x + y * y);
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+ }
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+
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+ /// Get the length squared. For performance, use this instead of
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+ /// b2Vec2::Length (if possible).
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+ float LengthSquared() const
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+ {
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+ return x * x + y * y;
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+ }
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+
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+ /// Convert this vector into a unit vector. Returns the length.
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+ float Normalize()
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+ {
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+ float length = Length();
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+ if (length < __FLT_EPSILON__)
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+ {
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+ return 0.0f;
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+ }
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+ float invLength = 1.0f / length;
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+ x *= invLength;
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+ y *= invLength;
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+
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+ return length;
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+ }
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+
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+ /// Does this vector contain finite coordinates?
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+ bool IsValid() const
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+ {
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+ return b2IsValid(x) && b2IsValid(y);
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+ }
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+
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+ /// Get the skew vector such that dot(skew_vec, other) == cross(vec, other)
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+ b2Vec2 Skew() const
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+ {
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+ return b2Vec2(-y, x);
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+ }
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+
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+ float x, y;
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+};
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+
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+/// Add two vectors component-wise.
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+inline b2Vec2 operator + (const b2Vec2& a, const b2Vec2& b)
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+{
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+ return b2Vec2(a.x + b.x, a.y + b.y);
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+}
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+
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+/// Subtract two vectors component-wise.
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+inline b2Vec2 operator - (const b2Vec2& a, const b2Vec2& b)
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+{
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+ return b2Vec2(a.x - b.x, a.y - b.y);
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+}
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+
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+inline b2Vec2 operator * (float s, const b2Vec2& a)
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+{
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+ return b2Vec2(s * a.x, s * a.y);
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+}
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+
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+inline bool operator == (const b2Vec2& a, const b2Vec2& b)
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+{
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+ return a.x == b.x && a.y == b.y;
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+}
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+
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+inline bool operator != (const b2Vec2& a, const b2Vec2& b)
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+{
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+ return a.x != b.x || a.y != b.y;
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+}
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+
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+inline float b2Distance(const b2Vec2& a, const b2Vec2& b)
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+{
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+ b2Vec2 c = a - b;
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+ return c.Length();
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+}
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+
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+/// Perform the cross product on two vectors. In 2D this produces a scalar.
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+inline float b2Cross(const b2Vec2& a, const b2Vec2& b)
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+{
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+ return a.x * b.y - a.y * b.x;
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+}
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+
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+/// Perform the dot product on two vectors.
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+inline float b2Dot(const b2Vec2& a, const b2Vec2& b)
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+{
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+ return a.x * b.x + a.y * b.y;
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+}
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+
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+#endif
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