In the ProBuilder language, the term Undefined is used to set a variable’s value to an undefined state. By default, a variable that is not explicitly assigned a value is equal to 0. Setting a variable to Undefined makes it invisible and unusable in calculations. This is particularly useful in scenarios where you need to indicate that a variable’s value is not currently set or known.

myvariable = Undefined

Definition and Purpose:

The Undefined keyword is used to explicitly clear a variable’s default value. Since variables are not initialized in ProBuilder and start at 0 by default, assigning Undefined prevents the variable from acting as a 0 initially. Important: Undefined can only be assigned to a variable once, usually at the very beginning of the code. Once the variable is assigned a real numerical value, it cannot be reverted back to Undefined.

Syntax:

• The syntax for setting a variable to undefined is straightforward: simply use the variable name followed by an equals sign and the keyword Undefined.

Example:

myPrice = Undefined
if condition1 then
    myPrice = close
endif

// Note: You cannot directly test if a variable equals Undefined.
// Instead, since undefined is treated as 0 in boolean evaluations, you can test if it equals 0.
if myPrice = 0 then
    // Perform specific actions when myPrice has not been set yet
endif

In this example, the variable myPrice is initially set to Undefined to avoid it being equivalent to 0 from the start. Depending on a condition (condition1), myPrice may later be assigned the value of the current closing price. Since Undefined cannot be tested directly, the script checks if myPrice is 0 to decide whether to perform certain actions.

Additional Information:

• Using Undefined is a good practice to avoid logical errors in scripts where you don’t want a variable to default to 0.
• Limitation: Undefined can only be assigned to a variable a single time. You cannot reset a variable to Undefined later in the execution.
• Variables set to Undefined are not drawn on the chart and do not impact indicators scaling.