Similar to a Worksheet Window, an SPL hot variable links a formula to a variable. When a dependent element of the formula changes, the hot variable automatically re-evaluates. Hot variables are assigned with the := operator. For example,
svar = integ(w1)
hvar := integ(w1)
The standard variable svar is assigned the series that results by integrating W1. The hot variable hvar is assigned the formula integ(w1). The value of hvar is also the series that results by integrating W1. However, when the value of Window 1 changes, the value of hvar automatically updates, but svar does not.
All hot variables are global, thus a hot variable and a standard global variable cannot have the same name. Unlike a window, hot variables can assume any of the data types supported by standard variables.
To automatically update, the formula of a hot variable must be dependent on some combination of windows and/or other hot variables.