## Functions

Function: int gsl_diff_central (const gsl_function *f, double x, double *result, double *abserr)
  This function computes the numerical derivative of the function f at the point x using an adaptive central difference algorithm. The derivative is returned in result and an estimate of its absolute error is returned in abserr.

Function: int gsl_diff_forward (const gsl_function *f, double x, double *result, double *abserr)
  This function computes the numerical derivative of the function f at the point x using an adaptive forward difference algorithm. The function is evaluated only at points greater than x and at x itself. The derivative is returned in result and an estimate of its absolute error is returned in abserr. This function should be used if f(x) has a singularity or is undefined for values less than x.

Function: int gsl_diff_backward (const gsl_function *f, double x, double *result, double *abserr)
  This function computes the numerical derivative of the function f at the point x using an adaptive backward difference algorithm. The function is evaluated only at points less than x and at x itself. The derivative is returned in result and an estimate of its absolute error is returned in abserr. This function should be used if f(x) has a singularity or is undefined for values greater than x.