Introduction

This section describes the options that you can select in response to the ? prompt, which is displayed after the debugger prints out a goal. The options are one-letter mnemonics, some of which optionally can be followed by a decimal integer. Any layout characters are ignored up to the next newline.

The most important option to remember is h (for help). When you type h, the following list of available options is displayed:

     Debugging options:
     
     <cr>   creep      p      print         r [i]  retry i      @    command
      c     creep      w      write         f [i]  fail i       b    break
      l     leap       d      display                           a    abort
      s [i] skip i                                              h    help
      z     zip        g [n]  n ancestors   +      spy pred     ?    help
      n     nonstop    < [n]  set depth     -      nospy pred   =    debugging
      q     quasi-skip .      find defn     e      raise_exception
     

These options provide a number of different functions, which fall into the following classes:

Basic control

he basic ways of continuing with the execution

Printing

howing the goal, or its ancestors, in various ways

Advanced control

ffecting control flow

Environment

hanging spypoints, executing commands, breaking and aborting, access to source code

Help

howing the debugger state and listing options

Each of the options is described below.