### 10.4 Combination properties

Function: size_t gsl_combination_n (const gsl_combination * c)

  This function returns the range (n) of the combination c.

Function: size_t gsl_combination_k (const gsl_combination * c)

  This function returns the number of elements (k) in the combination c.

Function: size_t * gsl_combination_data (const gsl_combination * c)

  This function returns a pointer to the array of elements in the combination c.

Function: int gsl_combination_valid (gsl_combination * c)

  This function checks that the combination c is valid. The k elements should lie in the range 0 to n-1, with each value occurring once at most and in increasing order.