void fit(double x[], double y[], int ndata, double sig[], int mwt, double *a,
	double *b, double *siga, double *sigb, double *chi2, double *q);
double gammq(double a, double x);
double gammln(double xx);
void gcf(double *gammcf, double a, double x, double *gln);
void gser(double *gamser, double a, double x, double *gln);

void nrerror(char error_text[]);


double *vector(long size);
void free_vector(double *v);
int *ivector(long size);
void free_ivector(int *v);
double **matrix(long rows, long cols);
void free_matrix(double **m);


static double sqrarg;
#define SQR(a) ((sqrarg=(a)) == 0.0 ? 0.0 : sqrarg*sqrarg)