Ronni Grapenthin - Tools (he / him / his) email:

University of Alaska Fairbanks Geophysical Institute 2156 Koyukuk Drive Fairbanks, AK-99775

t_debug - Debuging output in Matlab

When it comes to debugging I prefer the approach described by Brian Kernighan and Rob Pike in "The Practice of Programming":

"... we find stepping through a program less productive than thinking harder and adding output statements and self-checking code at critical places. Clicking over statements takes longer than scanning the output of judiciously-placed displays. It takes less time to decide where to put print statements than to single-step to the critical section of code, even assuming we know where that is. More important, debugging statements stay with the program; debugging sessions are transient."

To allow for debugging statements that stay with the program and can be switched on and off, I wrote two very simple Matlab functions (t_debug.m, print_debug.m). Here is how they work:

	>> t_debug on
	>> print_debug('t_debug is on');
	DEBUG: t_debug is on

	>> t_debug
	DEBUG state: 1

	>> t_debug off
	>> print_debug('This should not print');

	>> t_debug offff
	Warning: USE: debug(mode) with mode='on', 'off', or a numeric value to
	set debugging to a certain level. You used 'offff'. 
	> In t_debug at 54

	>> t_debug(10)
	>> print_debug('t_debug prints up to level 10', 9)
	DEBUG: (L=9)	t_debug prints up to level 10
	>> print_debug('t_debug prints up to level 10 (this won''t print)', 11)
	>> print_debug('t_debug prints up to level 10')
	DEBUG: t_debug prints up to level 10

	>> t_debug
	DEBUG state: 10
	

In t_debug I make use of the global preferences by introducing a group 'runmode' with preference 'debug' that's being set to 'true' or 'false' or 'number' when debug is 'on' or 'off' or N, respectively. print_debug checks the state of 'debug' in 'runmode' and displays the text it get's as a parameter:

	
	PRINT_DEBUG
	To set a program to debug mode use: 
	           t_debug on
	To exit debug mode:
	           t_debug off
	
	To use multi-level debugging output:
	           t_debug(N)             %where N=0..inf
	           print_debug(...,level) %where level <= N
	Here, 
	           N=0 represents 'off', i.e. no debugging output, 
	           N=1 and N=inf represents 'on', i.e. full debugging output
	

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