The organization principle evolved over two decades from many good and bad experiences. It has the advantage that, with an adaptation of just the bridge expression, we can use one and the same program with different GUIs and vice versa. Furthermore, the construction of views requires different tools than does the construction of models. Constructing views is a labor-intensive effort and involves graphical design, but fortunately, it is often possible to generate large portions automatically. The construction of models, in contrast, will always demand a serious program design effort.
Figure specifies the operations that the teachpack provides.
The GUI manager is represented by the function create-window . Its contract and purpose statement are instructive. They explain that we create a window from a list. The function arranges these lists in a corresponding number of rows on the visible window. Each row is specified as a list of gui-item s.