Note: Debug requires a prokey, and will fail with domain error if a prokey is not set. For more information, see products.
This is a preliminary version of Debug. This version is not complete, and requires changes in the J engine before it can provide all the facilities we envision. See also outstanding problems that you should be aware of these when using the debugger.
Debug is an extension to the facilities provided by the debug foreign conjunction. After Debug is turned on, then if execution is halted because of a stop or execution error, the Debug window shows the current execution environment.
Panels in the Debug window show the code being executed, the stack, and values of various names:
any watch names
the arguments of the current definition
any names on the current line of code.
For an introduction to Debug, see the Debug lab.
For information on the debug foreign conjunction, see the Dictionary entry for the 13!:x family, and script system\main\debug.ijs.
To load Debug, use menu Run|Debug..., or press Ctrl-K when the J session has focus.
This loads the debug.ijs script, displays the Debug window, enables suspension (dbr 1), and sets the debug latent expression (dblxs) to run the verb debug in the jdebug locale.
Then run your program. If execution is halted because of a stop or execution error, the execution state is shown in the Debug window. Several commands let you step through the execution session.
To turn Debug off and disable suspension, close the Debug window.
Debug is active when suspension is on, and the debug latent expression is set. The Debug window is displayed when Debug is activated, so this provides a visual indication that Debug is active.
However, if you change either of these directly, for example, by entering:
dbr 0
then Debug will no longer be active, even if the Debug window is still displayed. You can reactivate Debug by pressing Ctrl-K.