-=(_:_:)
Subtracts one demand from another, and assigns the result to the first demand.
Declaration
static func -= (lhs: inout Subscribers.Demand, rhs: Subscribers.Demand)Discussion
When subtracting any value (including .unlimited) from .unlimited, the result is still .unlimited. Subtracting .unlimited from any value (except .unlimited) results in .max(0). A negative demand is impossible; when an operation would result in a negative value, Combine adjusts the value to .max(0).