anchor.diff:  
       case_id = 1
       name = "from_linearized"
  -    nan_val = ieee_value(nan_val, ieee_quiet_nan)
   
       ! CASE 1: Basic test of not-very-linearized quadratics.
       nodes1(1, :) = 0
  
positive.code:     start_node2 = nodes2(:1, :)
      end_node2 = nodes2(3:, :)
      ! NOTE: This curve isn't close to linear, but that's OK.
      error2 = nan_val
  
      call from_linearized( &
           error1, 0.0_dp, 1.0_dp, start_node1, end_node1, 3, nodes1, &
  
negative.code:     nodes2(3, :) = 3
      start_node2 = nodes2(:1, :)
      end_node2 = nodes2(3:, :)
      call linearization_error( &
           3, 2, nodes2, error2)
  
      call from_linearized( &
           error1, 0.0_dp, 1.0_dp, start_node1, end_node1, 2, nodes3, &
  