typedef struct
{
  int xsv, ysv;
  double dx, dy;
} LatticePoint2D;

typedef struct
{
  double dx, dy;
} Grad2;

typedef struct
{
  short *perm;
  Grad2 *permGrad2;
} OpenSimplexGradients;

typedef struct
{
  Grad2 *GRADIENTS_2D;
  LatticePoint2D **LOOKUP_2D;
} OpenSimplexEnv;

OpenSimplexEnv *initOpenSimplex();
OpenSimplexGradients *newOpenSimplexGradients(OpenSimplexEnv *ose, long seed);
double noise2(OpenSimplexEnv *ose, OpenSimplexGradients *osg, double x, double y);
double noise2_XBeforeY(OpenSimplexEnv *ose, OpenSimplexGradients *osg, double x, double y);