c++ - Find number of rows/columns in a GSL matrix? -

say have gsl_matrix * a. want write function retrieves e.g. number of rows in matrix, without having access else besides object itself.

example:

int num_rows(gsl_matrix * a){     //some operation(s) on find number of rows in matrix     //store number in int r     return r; } 

what write me?

from https://www.gnu.org/software/gsl/manual/html_node/matrices.html

gsl_matrix defined as:

typedef struct {   size_t size1;   size_t size2;   size_t tda;   double * data;   gsl_block * block;   int owner; } gsl_matrix; 

and

the number of rows size1. range of valid row indices runs 0 size1-1. size2 number of columns. range of valid column indices runs 0 size2-1. physical row dimension tda, or trailing dimension, specifies size of row of matrix laid out in memory.

so if want number of rows in a use:

int num_rows(gsl_matrix * a){     int r = a->size1;     return r; }