solve-concurrent/it.unibo.tuprolog.solve.concurrent.fsm/StatePrimitiveSelection

StatePrimitiveSelection

data class StatePrimitiveSelection(val context: ConcurrentExecutionContext) : AbstractState

"Primitive Selection": inspects ConcurrentExecutionContext.currentGoal and either raises an it.unibo.tuprolog.solve.exception.error.InstantiationError/it.unibo.tuprolog.solve.exception.error.TypeError (goal is a variable or not callable), invokes the matching it.unibo.tuprolog.solve.primitive.Primitive if one is registered for the goal's signature in it.unibo.tuprolog.solve.library.Runtime, or falls through to StateRuleSelection otherwise (the goal is a user-/library-defined predicate).

When a primitive is invoked, every response it lazily produces becomes its own StatePrimitiveExecution: this is one of the two points (the other being StateRuleSelection) where a single state can fan out into many concurrently-explored successors, e.g. for a backtracking primitive like between/3 that can succeed several times.

Constructors

constructor(context: ConcurrentExecutionContext)

Properties

context

open override val context: ConcurrentExecutionContext

The execution context this state operates on.

isEndState

open val isEndState: Boolean

Whether this state is a terminal one for the current branch, 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: ConcurrentExecutionContext = this.context): StatePrimitiveSelection

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

open override fun next(): Iterable<State>

Computes every state this branch may transition into from here, one per alternative (matching clause, disjunct, primitive solution, ...) available at this point; empty only for EndStates. Each element is meant to be explored independently (and, in :solve-concurrent's solver, concurrently) of the others.