solve-classic/it.unibo.tuprolog.solve.classic.fsm/StateBacktracking

StateBacktracking

data class StateBacktracking(val context: ClassicExecutionContext) : AbstractState

"Backtracking", the central hub of the state machine: if ClassicExecutionContext.choicePoints is empty (or exhausted), moves to StateEnd emitting a negative solution; otherwise it walks the choice-point queue's pathToRoot for the nearest choice point that still has an alternative, restores that saved execution-context lineage (see it.unibo.tuprolog.solve.classic.ChoicePointContext.backtrack), and resumes at either StatePrimitiveExecution or StateRuleExecution, depending on which kind of alternative was pending.

Constructors

StateBacktracking

constructor(context: ClassicExecutionContext)

Properties

context

open override val context: ClassicExecutionContext

The execution context this state operates on.

isEndState

open val isEndState: Boolean

Whether this state is a terminal one for the current resolution step, i.e. an EndState.

Functions

asEndState

open fun asEndState(): EndState?

This state as an EndState, or null if isEndState is false.

castToEndState

open fun castToEndState(): EndState

This state as an EndState.

clone

open override fun clone(context: ClassicExecutionContext = this.context): StateBacktracking

Returns a copy of this state, replacing context with the given one (defaulting to the current context).

open override fun next(): State

Computes the state the machine transitions into from here -- a pure function of context.