Chapter 13. Reflection and Debugging

This chapter describes commands that give you a view into the interpreter. The history command and a simple debugger are useful during development and debugging. The info command provides a variety of information about the internal state of the Tcl interpreter. The time command measures the time it takes to execute a command. Tcl commands discussed are: clock, info, history, and time.

Reflection provides feedback to a script about the internal state of the interpreter. This is useful in a variety of cases, from testing to see whether a variable exists to dumping the state of the interpreter. The info command provides lots of different information about the interpreter.

The clock command returns the time, formats time values, does time calculations, and parses time strings. It is a great tool all by itself. It also provides high-resolution timer information for precise measurements.

Interactive command history is the third topic of the chapter. The history facility can save you some typing if you spend a lot of time entering commands interactively.

Debugging is the last topic. The old-fashioned approach of adding puts commands to your code is often quite useful. For tough problems, however, a real debugger is invaluable. The Tcl Dev Kit toolset from ActiveState include a high quality debugger and static code checker. The tkinspect program is an inspector that lets you look into the state of a Tk application. It can hook up to any Tk application dynamically, so it proves quite useful.