Your parameter initializations are not recursive. In Matlab, you can execute any Matlab code statement (the parameter definitions and the content within the initval-block are Matlab compatible code) by selecting it using your mouse and the either right-click and choose “Evaluate selection” or pressing the shortcut F9. Try using F9 to execute the initializations before the model-block to see that phi_f uses A in its definition, but A is only defined later on.