Variable

A Variable is a BDD node representing a Boolean variable.

Properties

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high is the BinaryDecisionDiagram that leads to a 1-terminal (a true terminal), i.e. the sub-diagram to follow when value is assigned true.

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open override val isTerminal: Boolean

Returns true if this node is a Terminal node.

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open override val isVariable: Boolean

Returns true if this node is a Variable node.

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abstract val low: BinaryDecisionDiagram<T>

low is the BinaryDecisionDiagram that leads to a 0-terminal (a false terminal), i.e. the sub-diagram to follow when value is assigned false.

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abstract val value: T

value represents the boolean variable

Functions

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open override fun <E> accept(visitor: BinaryDecisionDiagramVisitor<T, E>): E

Accepts an instance of BinaryDecisionDiagramVisitor as for the visitor pattern. This is the method of preference for exploring the inner structure of the diagram, since it distinguishes between Terminal and Variable nodes without runtime type checks by the caller.

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Performs the "And" binary boolean operation over two BinaryDecisionDiagrams. The result is a Reduced Ordered Binary Decision Diagram (ROBDD) representing the logical conjunction of the Boolean formulas encoded by the two diagrams.

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fun <T : Comparable<T>, E> BinaryDecisionDiagram<T>.andThenExpansion(that: BinaryDecisionDiagram<T>, expansionFalseTerminal: E, expansionTrueTerminal: E, expansionOperator: (node: T, low: E, high: E) -> E): Pair<BinaryDecisionDiagram<T>, E>

Performs the "And" binary boolean operation over two BinaryDecisionDiagrams and computes a value using the Shannon Expansion over the result. The result is an instance of Pair of which Pair.first is the Reduced Ordered Binary Decision Diagram (ROBDD) produced by the operation, and Pair.second is the value of type E computed with the Shannon Expansion.

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Returns true if the BinaryDecisionDiagram has at least one variable element, i.e. it is not just a Terminal.

fun <T : Comparable<T>> BinaryDecisionDiagram<T>.any(predicate: (T) -> Boolean): Boolean

Returns true if the BinaryDecisionDiagram has at least one Variable element matching the given predicate. Used e.g. by it.unibo.tuprolog.solve.problog.lib.knowledge.impl.BinaryDecisionDiagramExplanation.containsAnyNotGroundTerm as diagram.any { !it.isGround }, to detect explanations that still contain unbound Prolog terms.

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Applies the "Apply" construction algorithm over BinaryDecisionDiagrams using a given unary boolean operator. The result is a Reduced Ordered Binary Decision Diagram (ROBDD).

Applies the "Apply" construction algorithm over two BinaryDecisionDiagrams using a given binary boolean operator. The result is a Reduced Ordered Binary Decision Diagram (ROBDD).

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fun <T : Comparable<T>, E> BinaryDecisionDiagram<T>.applyThenExpansion(unaryOp: (Boolean) -> Boolean, expansionFalseTerminal: E, expansionTrueTerminal: E, expansionOperator: (node: T, low: E, high: E) -> E): Pair<BinaryDecisionDiagram<T>, E>

Applies the "Apply" construction algorithm over BinaryDecisionDiagrams using a given unary boolean operator, and computes a value using the Shannon Expansion over the result. The result is an instance of Pair of which Pair.first is the Reduced Ordered Binary Decision Diagram (ROBDD) produced by the operation, and Pair.second is the value of type E computed with the Shannon Expansion.

fun <T : Comparable<T>, E> BinaryDecisionDiagram<T>.applyThenExpansion(that: BinaryDecisionDiagram<T>, binaryOp: (Boolean, Boolean) -> Boolean, expansionFalseTerminal: E, expansionTrueTerminal: E, expansionOperator: (node: T, low: E, high: E) -> E): Pair<BinaryDecisionDiagram<T>, E>

Applies the "Apply" construction algorithm over two BinaryDecisionDiagrams using a given binary boolean operator, and computes a value using the Shannon Expansion over the result. The result is an instance of Pair of which Pair.first is the Reduced Ordered Binary Decision Diagram (ROBDD) produced by the operation, and Pair.second is the value of type E computed with the Shannon Expansion.

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Returns the number of Variable nodes contained in a BinaryDecisionDiagram. Note that, since a node can be shared by multiple parents (e.g. in a reduced diagram built by BinaryDecisionDiagramBuilder.reducedOf), a shared node is counted once for every path that reaches it, not once overall.

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fun <T : Comparable<T>, E> BinaryDecisionDiagram<T>.expansion(falseTerminal: E, trueTerminal: E, operator: (node: T, low: E, high: E) -> E): E

Applies a given operation over a BinaryDecisionDiagram using the Shannon Expansion. The result is a reduction of a given diagram, determined by applying an operation recursively over a BDD with bottom-up order: each Terminal is mapped to falseTerminal/trueTerminal, and each Variable is folded with operator, receiving the already-computed E values of its low/high sub-diagrams.

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Returns a BinaryDecisionDiagram containing nodes of applying the given transform function to each element in the original BinaryDecisionDiagram. The internal structure of the diagram is maintained. Used e.g. by it.unibo.tuprolog.solve.problog.lib.knowledge.impl.BinaryDecisionDiagramExplanation.apply to rewrite the Prolog terms held by every variable of an explanation (e.g. after applying a substitution), as diagram.map { transformation(it) }.

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Performs the "Not" unary boolean operation over a BinaryDecisionDiagram. The result is a Reduced Ordered Binary Decision Diagram (ROBDD) representing the logical negation of the Boolean formula encoded by this diagram.

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fun <T : Comparable<T>, E> BinaryDecisionDiagram<T>.notThenExpansion(expansionFalseTerminal: E, expansionTrueTerminal: E, expansionOperator: (node: T, low: E, high: E) -> E): Pair<BinaryDecisionDiagram<T>, E>

Performs the "Not" unary boolean operation over a BinaryDecisionDiagram and computes a value using the Shannon Expansion over the result. The result is an instance of Pair of which Pair.first is the Reduced Ordered Binary Decision Diagram (ROBDD) produced by the operation, and Pair.second is the value of type E computed with the Shannon Expansion.

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Performs the "Or" binary boolean operation over two BinaryDecisionDiagrams. The result is a Reduced Ordered Binary Decision Diagram (ROBDD) representing the logical disjunction of the Boolean formulas encoded by the two diagrams.

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fun <T : Comparable<T>, E> BinaryDecisionDiagram<T>.orThenExpansion(that: BinaryDecisionDiagram<T>, expansionFalseTerminal: E, expansionTrueTerminal: E, expansionOperator: (node: T, low: E, high: E) -> E): Pair<BinaryDecisionDiagram<T>, E>

Performs the "Or" binary boolean operation over two BinaryDecisionDiagrams and computes a value using the Shannon Expansion over the result. The result is an instance of Pair of which Pair.first is the Reduced Ordered Binary Decision Diagram (ROBDD) produced by the operation, and Pair.second is the value of type E computed with the Shannon Expansion.

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Formats a BinaryDecisionDiagram using Graphviz DOT notation (https://graphviz.org/). This provides a fast and widely supported solution to visualize the contents of a BDD.