The stepper

Macintosh Common Lisp provides the step macro as a simple way of stepping through the execution of an expression, subexpression by subexpression.

You can use the step macro on compiled functions only if their definitions have been retained. Function definitions are retained if the function is compiled with the variable *save-definitions* set to a true value. If the function was compiled with *save-definitions* set to nil, the value must be changed and the function must be recompiled before it can be stepped through.

The step macro is usually called only from the top level. You can invoke internal stepping through options to the trace macro.

It is not generally possible to step through code that requires the use of without-interrupts or code that uses the Macintosh graphics interface.

Figure 4-7 Stepping through the factorial function

Gettmg Started with MCL - 19 OCT 1996

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