status: draft (2023-11-13)
keywords: Exceptions
See also SRFI 255: Restarting conditions.When an exceptional situation is encountered by a program, it usually creates a condition object describing the situation and then passes control to an exception handler. The signaler and handler are two different parts of a system, between which there is a barrier of abstraction. In order to recover gracefully and flexibly from exceptional situations, however, the signaler can provide multiple ways by which the handler can restart the computation, some of which may require extra input. Often, the decision of which method of recovery to choose is left up to a human user, who may be prompted for the input needed to recover. This SRFI proposes a mechanism called restarters which uses a new type of condition object and an associated exception handler to encapsulate the information necessary to restart a computation. We also describe the behavior and interface of interactor procedures, which implement interactive restarts.