def add_variables(vars)
      # Allocate space for the new variables
      ret = LPSolve.resize_lp(@ptr, @constraints.length,
                              @variables.length + vars.length)
      fail if ret != 1

      # Store all the variables in the model
      vars.each { |var| store_variable var }
    end
def add_variables(vars)
      # Allocate space for the new variables
      ret = LPSolve.resize_lp(@ptr, @constraints.length,
                              @variables.length + vars.length)
      fail if ret != 1

      # Store all the variables in the model
      vars.each { |var| store_variable var }
    end
Add multiple variables to the model simultaneously