Checkpoint

src/prolog/builtins/control.kt

@@ -1,77 +0,0 @@
-package prolog.builtins
-
-import prolog.ast.terms.*
-import prolog.logic.Substituted
-
-/**
- * Always fail.
- */
-class Fail : Atom("fail"), Body {
-    override fun prove(subs: Substituted): Sequence<Substituted> = emptySequence()
-}
-
-/**
- * Same as fail, but the name has a more declarative connotation.
- */
-typealias False = Fail
-
-/**
- * Always succeed.
- */
-class True : Atom("true"), Body {
-    override fun prove(subs: Substituted): Sequence<Substituted> = sequenceOf(emptyMap())
-}
-
-// TODO Repeat/0
-
-// TODO !/0 (Cut)
-
-/**
- * Conjunction (and). True if both Goal1 and Goal2 are true.
- */
-class Conjunction(leftOperand: Operand, rightOperand: Operand) : Operator(Atom(","), leftOperand, rightOperand) {
-    override fun prove(subs: Substituted): Sequence<Substituted> = sequence {
-        if (leftOperand != null) {
-            leftOperand.prove(subs).forEach { left ->
-                rightOperand.prove(subs + left).forEach { right ->
-                    yield(left + right)
-                }
-            }
-        } else {
-            yieldAll(rightOperand.prove(subs))
-        }
-    }
-}
-
-/**
- * Disjunction (or). True if either Goal1 or Goal2 succeeds.
- */
-open class Disjunction(leftOperand: Operand, rightOperand: Operand) : Operator(Atom(";"), leftOperand, rightOperand) {
-    override fun prove(subs: Substituted): Sequence<Substituted> = sequence {
-        if (leftOperand != null) {
-            yieldAll(leftOperand.prove(subs))
-        }
-        yieldAll(rightOperand.prove(subs))
-    }
-}
-
-@Deprecated("Use Disjunction instead")
-class Bar(leftOperand: Operand, rightOperand: Operand) : Disjunction(leftOperand, rightOperand)
-
-// TODO ->
-
-// TODO *->
-
-/**
- * True if 'Goal' cannot be proven.
- */
-class Not(goal: Goal) : Operator(Atom("\\+"), rightOperand = goal) {
-    override fun prove(subs: Substituted): Sequence<Substituted> {
-        // If the goal can be proven, return an empty sequence
-        if (rightOperand.prove(subs).toList().isNotEmpty()) {
-            return emptySequence()
-        }
-        // If the goal cannot be proven, return a sequence with an empty map
-        return sequenceOf(emptyMap())
-    }
-}