How to Debug Code

VisionScript features a built-in debugger for understanding how your code works and finding the source of errors.

The debugger triggers when a Breakpoint[] runs in a program. This command stops your code in place and creates an interactive environment in which you can debug.

To debug a program, first add a breakpoint to your script:

Load["./image.jpg"]
Detect["cat"]
Count[]
Breakpoint[]
Say[]

Then, run your program:

visionscript program.vic

When your program reaches the breakpoint, the debugger will trigger.

The debugger looks like this:

[n,p,q,s,r,h] VisionScript Debug Mode >

The letters at the beginning are commands, which mean:

• n: Prints the abstract syntax tree for the current line. Run the current line and go to the next one.
• p: Go to the previous line.
• q: Quit the debugger. This will start running your code until another breakpoint is run, if any. If no breakpoints are run, the program will run to completion.
• r: List values in state that you can access.
• s [state_value]: Show the value of a state. For example, s detections_stack will show the value of the detections_stack state.
• h: Show help.