Getting the Bugs Out :: M-File Programming (Programming)

Programming

Getting the Bugs Out

In all but the simplest programs, you are likely to encounter some type of unexpected behavior when you run the program for the first time. Program defects can show up in the form of warning or error messages displayed in the command window, programs that hang (never terminate), inaccurate results, or some number of other symptoms. This is where the second functionality of the MATLAB Editor/Debugger becomes useful.

The MATLAB Debugger enables you to examine the inner workings of your program while you run it. You can stop the execution of your program at any point and then continue from that point, stepping through the code line by line and examining the results of each operation performed. You have the choice of operating the debugger from the Editor window that displays your program, from the MATLAB command line, or both.

The Debugging Process

You can step through the program right from the start if you want. For longer programs, you will probably save time by stopping the program somewhere in the middle and stepping through from there. You can do this by approximating where the program code breaks and setting a stopping point (or breakpoint) at that line. Once a breakpoint has been set, start your program from the MATLAB command prompt. MATLAB opens an Editor/Debugger window (if it is not already open) showing a green arrow pointing to the next line to execute.

From this point, you can examine any values passed into the program, or the results of each operation performed. You can step through the program line by line to see which path is taken and why. You can step into any functions that your program calls, or choose to step over them and just see the end results. You can also modify the values assigned to a variable and see how that affects the outcome.

To learn about using the MATLAB Debugger, see Debugging and Improving M-Files in the Desktop Tools and Development Environment documentation. Type help debug for a listing of all MATLAB debug functions.

For programming tips on how to debug, see Debugging.

Program Development Cleaning Up the Program