--[=[
	Starts the observable with the given value from the callback

	http://reactivex.io/documentation/operators/start.html

	@param callback function
	@return (source: Observable) -> Observable
]=]

function Rx.start(callback)
	return function(source)
		assert(Observable.isObservable(source), "Bad observable")

		return Observable.new(function(sub)
			sub:Fire(callback())

			return source:Subscribe(sub:GetFireFailComplete())
		end)
	end
end
