STK_HRECT creates an hyper-rectangle object

 CALL: B = stk_hrect (D)
 CALL: B = stk_hrect (D, COLNAMES)

   creates an object representing a D-dimensional unit hypercube, [0; 1] ^ D.

   The second (optional) argument can be used to provide variable names.

 CALL: B = stk_hrect (X)
 CALL: B = stk_hrect (X, COLNAMES)

   creates an object representing a D-dimensional hyperrectangle with lower
   bounds X(1, :) and upper bounds X(2, :). The input X must be a 2xD
   numerical array.

 NOTE: class hierarchy

   An stk_hrect object is two-row stk_dataframe object, with row names
   'lower_bounds' and 'upper_bounds'.

 See also: stk_dataframe, stk_boundingbox