Absolutely! We use this all the time!
Here's the scenario -- we are designing a Behavioral Experiment, with a lot of Bells and Whistles. We want the User (who knows nothing about LabVIEW, but everything about the Experiment) to be able to "program" the set of stimuli delivered.
An example would be Sound Localization. Suppose I could position a loud speaker in an arc in front of the subject (in the dark) and play a sound through it. Suppose also I had an LED on the speaker that I could flash, a movable Laser that I could position somewhere as another target, and a Laser Pointer that I could illuminate when the Subject was supposed to "point to where you think the sound is coming from". I also say "If you see a flashing light, but no sound, point to the light".
OK. The Experimenter is given an Excel Worksheet to fill out -- the Rows are the individual Experiment Trials for the Subject to perform, the Columns define what happens during a Trial. To help the Experimenter, I group "modalities" together. All Time parameters are given in milliseconds. Many of the Stimuli have a pair of parameters -- Delay (from Start of Stimulus Epoch) and Duration (once on). Consider the following cases for, say, Sound:
Delay = 0, Duration = 1000 1 second sound, starts immediately
Delay = 1000, Duration = 1000 1 second sound, starts after 1 second (i.e. one second off, one second on, then off)
Delay = -1, Duration = anything This is the "Wait Forever" case that effectively means "Don't use this stimulus"
Delay = 0, Duration = -1 This is the "Start and don't stop" (until you Press the Button that ends the Trial)
Delay = 0, Duration = 0 No sound (because a Duration of 0 is effectively "Stop Immediately" = "Never Start")
Now, in principle, I could have said "Put in a delay of a million if you want (for all practical purposes) to never start", but "reserving" the special values of -1 (forever) and 0 (never) are much more mnemonic for everyone.
I introduced this scheme after a complete overhaul of an existing code base written in LabVIEW 7 that had been in use for about 6 years. The students who were going to use the code were wildly enthusiastic about the new changes, and found it much more logical and easier to use -- my colleagues on the faculty who initially set out the specifications of the original code a decade ago were skeptical (but, as the students noted, "They'll Never Know the Difference ...").
Bob Schor
P.S. -- I do carefully explain that if they choose to keep the Subject in the room for 7 weeks waiting for the sound to occur, it will occur, but they usually use other "End of Trial" criteria to end really end the Trial earlier. Indeed, I have code that checks for "Forever" and, indeed, does not schedule a 7-week delay, so "Don't Even Think About It ...". So far, no one has been confused by this.
