Vars (Var Selectors)

Var is a small selector type used to read values from a ProcessContext by name.

Two Forms

1. Subcontext variable

Var(entity_ref, :name)

This reads :name from the subcontext of entity_ref.

Example:

counter = Counter()
Var(counter, :count)

2. Global variable

Var(:name)

This reads :name from context.globals.

So:

• Var(:process) reads context.globals.process
• Var(:algo) reads context.globals.algo
• Var(:lifetime) reads context.globals.lifetime

Common Use in Until

Var is commonly used with Processes.Until(...) to pick what value the stop condition should inspect.

Example with a subcontext variable:

counter = Counter()

lifetime = Processes.Until(x -> x >= 100, Var(counter, :count))

Example with a global variable (process object):

lifetime = Processes.Until(p -> loopidx(p) >= 10_000, Var(:process))

Var(:process) is useful when your stop rule depends on process-level state.

In Until/RepeatOrUntil, this function is a stop condition (true => stop, false => continue).