STEP.LSP

This file contains a simple Lisp single-step debugger. It started as an implementation of the "hook" example in chapter 20 of Steele's "Common Lisp". This version was brought up on Xlisp 1.7 for the Amiga, and then on VAXLISP.

When the package feature is compiled in, the debugger is in the TOOLS package.

To invoke: (step (whatever-form with args))

For each list (interpreted function call), the stepper prints the environment and the list, then enters a read-eval-print loop. At this point the available commands are:

(a list)<CR> evaluate the list in the current environment, print the result, and repeat.

: step into the called function
: step over the called function.

If the stepper comes to a form that is not a list it prints the form and the value, and continues on without stopping.

Note that stepper commands are executed in the current environment. Since this is the case, the stepper commands can change the current environment. For example, a SETF will change an environment variable and thus can alter the course of execution.

Global variables - newline, *hooklevel*

Functions/macros - while step eval-hool-function step-spaces step-flush

Note ? an even more powerful stepper package is in stepper.lsp (documented in stepper.doc).

XLISP-PLUS - Version 2.1g - Tom Almy tom.almy@tek.com - 18 JUL 94

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