Annotation-based program stepping

Traditionally, stepping is achieved by modifying the evaluator. In the approach presented here, stepping is achieved by annotating the user's program with calls to stepping procedures. This provides greater flexibility in the selection of which program sections the user is interested in stepping. In addition, the sections not selected are executed without overhead. Stepped program sections are visually highlighted inside the user's program editor, providing a sense of context. Stepping control mechanisms, such as the ability to execute until a certain point and then step, permit the user to navigate through a program in a precise and flexible manner. A prototype stepper based on this approach has been implemented.