solve-concurrent/it.unibo.tuprolog.solve.concurrent.stdlib.rule/NegationAsFailure

NegationAsFailure

sealed class NegationAsFailure : RuleWrapper<ExecutionContext>

A rule-based, two-clause implementation of negation as failure (\+/1): Fail tries X and, if it succeeds, cuts and fails; Success is the fallback clause that succeeds when Fail didn't. This is the same encoding :solve-classic uses, but here it is shadowed by the primitive it.unibo.tuprolog.solve.concurrent.stdlib.primitive.Naf registered under the same \+/1 signature in it.unibo.tuprolog.solve.concurrent.stdlib.DefaultBuiltins: primitives are looked up before rules (see it.unibo.tuprolog.solve.concurrent.fsm.StatePrimitiveSelection), so Fail/Success never actually run as long as that primitive stays registered.

Inheritors

Types

object Companion

object Fail : NegationAsFailure

\+(X) :- ensure_executable(X), call(X), !, fail. -- fails if X succeeds at least once.

object Success : NegationAsFailure

\+(X) :- true. -- the fallback clause, reached only if Fail didn't cut resolution short.

Properties

abstract override val Scope.body: Term

descriptionPair

val descriptionPair: Pair<Signature, Rule>

val functor: String

open override val Scope.head: List<Term>

override val implementation: Rule

val signature: Signature

Functions

override fun toString(): String