LabVIEW
Using the for loop iteration number as variable outside loop
To (badly) paraphrase a well-known saying, "What Changes Inside a For (or While) Loop, Stays Inside the For (or While) Loop". [As with every rule, there are exceptions ...]
The Principle of Data Flow (absolutely central to LabVIEW) says that functions (such as graphs, charts, and indicators) placed outside the Loop cannot show you changes that take place inside the loop (but see [statement] above) -- values only are exported from the loop when it exits. If you want to use/watch values that vary inside the loop, you need to put your indicator ... inside the loop!
Look at these three examples, all of which end with Rand being the final Random number and Count being the final Count (99 -- do you know why?).
The first example will display only one value, the final one. The second example will, in fact, display all 100 values, but they'll zip by so fast you'll only notice the last one. The final loop adds a 50 millisecond wait to let you see the numbers count up, and after 5 seconds, the loop will exit leaving the final values in the indicators.
[If you try this yourself, you'll notice that when you code the first example, the wire coming out of the For loop is not a "Last Value" tunnel, but an "Indexing" tunnel, looking like a square-within-a-square, building an array instead of the last value. You can right-click the tunnel and change it to a Last Value tunnel, which is what I did.]
Bob Schor
10 second analysis:
- way too many local variables and structure stacks (e.g. eliminate the inner loop in the lower part and place the shift regsiter on the outer loop).
- constantly converting between "scalars" and "arrays with one element" is just silly.
- use consistent representations.
- There is a "+1" perimitive
- ...
Also note that your lower loop run at a near infinite rate if the selector boolean is false, spinning the loop as fast as the computer allows, trying consume all available CPU and starving all other processes (e.g. the upper loop!).
Here's how the code of the lower loop could look like instead. (Personally, I would probably implement that logic into the upper loop and eliminate all locals.)
