This ProBuilder code snippet demonstrates how to use a WHILE loop to draw horizontal lines on a chart at fixed intervals of 100 points. The example is particularly useful for visualizing significant levels or grid lines on financial charts.

IF NOT DID THEN 
    NV = 0 
    while NV <= 30000 DO 
        drawhline(NV) coloured("cyan") 
        NV = NV + 100 
    wend 
    ONCE DID = 1 
ENDIF 
RETURN

The code snippet provided performs the following operations:

• Conditional Check: The IF NOT DID THEN condition checks if the variable DID is false (or not yet set). This ensures that the lines are only drawn once.
• Initialization: The variable NV is initialized to 0. This variable will be used to set the y-value of the horizontal lines.
• WHILE Loop: The loop continues as long as NV is less than or equal to 30000. Inside the loop, a horizontal line is drawn at the current value of NV using drawhline(NV) coloured("cyan"). The color cyan is specified for the line.
• Increment: Inside the loop, NV is incremented by 100 after each iteration. This increment sets the next level at which a horizontal line will be drawn.
• Loop Termination: Once NV exceeds 30000, the loop terminates.
• Flag Setting: After exiting the loop, DID is set to 1 by ONCE DID = 1. This prevents the loop from executing again on subsequent calculations or redraws of the chart.
• End of Conditional and Function: The ENDIF and RETURN statements mark the end of the conditional block and the function, respectively.

This example is a practical demonstration of controlling flow with loops and conditionals in ProBuilder, useful for tasks requiring repeated actions until a certain condition is met.