Adding Automatic Inference Reasoners

Beside the input sequent, reasoners of this type does not have any extra input and automatically applies an inference rule to the input sequent. As an example, consider the following inference rule (called IMP_R).

$\frac{H, P \vdash Q}{H \vdash P \limp Q}$

IMP_R

Declare the Reasoner

• Create a new plug-in project, e.g. org.eventb.contributors.seqprover.implinference. Deselect the plug-in options for "Generating an activator" and "Contribution to the UI".

• Add dependency on the project org.eventb.core.seqprover

• Add an extension for org.eventb.core.seqprover.reasoners for our implication rewrite reasoner, e.g.

<extension point="org.eventb.core.seqprover.reasoners">
  <reasoner
    class="org.eventb.internal.contributors.seqprover.implinference.AutoInference"
    id="autoInference"
    name="%autoInferenceName"/>
</extension>

(add the key autoInferenceName to the plugin.properties accordingly).

• We will use Tom to implement the reasoner class itself.

Implement the Reasoner

The following steps is for implementing the reasoner using Tom.

• Create a package within the src folder of the project with the name org.eventb.internal.contributors.seqprover.implinference.

• Create a Tom file within the newly created package with the name AutoInference.t.

• The content of the Tom file looks like this.

package org.eventb.internal.contributors.seqprover.implinference;

import java.math.BigInteger;
import java.util.ArrayList;
import java.util.Collection;
import java.util.List;
import java.util.Set;
import java.util.HashSet;

import org.eventb.core.ast.AssociativeExpression;
import org.eventb.core.ast.AssociativePredicate;
import org.eventb.core.ast.AtomicExpression;
import org.eventb.core.ast.BinaryExpression;
import org.eventb.core.ast.BinaryPredicate;
import org.eventb.core.ast.BoolExpression;
import org.eventb.core.ast.BoundIdentDecl;
import org.eventb.core.ast.BoundIdentifier;
import org.eventb.core.ast.DefaultFilter;
import org.eventb.core.ast.Expression;
import org.eventb.core.ast.Formula;
import org.eventb.core.ast.FormulaFactory;
import org.eventb.core.ast.FreeIdentifier;
import org.eventb.core.ast.Identifier;
import org.eventb.core.ast.IntegerLiteral;
import org.eventb.core.ast.IPosition;
import org.eventb.core.ast.LiteralPredicate;
import org.eventb.core.ast.PowerSetType;
import org.eventb.core.ast.Predicate;
import org.eventb.core.ast.ProductType;
import org.eventb.core.ast.QuantifiedExpression;
import org.eventb.core.ast.QuantifiedPredicate;
import org.eventb.core.ast.RelationalPredicate;
import org.eventb.core.ast.SetExtension;
import org.eventb.core.ast.SimplePredicate;
import org.eventb.core.ast.Type;
import org.eventb.core.ast.UnaryExpression;
import org.eventb.core.ast.UnaryPredicate;
import org.eventb.core.seqprover.eventbExtensions.Tactics;
import org.eventb.core.seqprover.IProverSequent;
import org.eventb.core.seqprover.IHypAction;
import org.eventb.core.seqprover.ProverFactory;
import org.eventb.core.seqprover.SequentProver;
import org.eventb.core.seqprover.IProofRule.IAntecedent;
import org.eventb.core.seqprover.eventbExtensions.Lib;
import org.eventb.core.seqprover.eventbExtensions.Tactics;
import org.eventb.internal.core.seqprover.eventbExtensions.AbstractAutoInference;

/**
 * Basic implementation for "automatic implication inference"
 */
@SuppressWarnings("unused")
public class AutoInference extends AbstractAutoInference {

  %include {Formula.tom}
	
  public String getReasonerID() {
    return "org.eventb.contributors.seqprover.implinference.autoInference";
  }
	
  @Override
  protected String getDisplayName() {
    return "Automatic deduction";
  }

  @Override
  protected IAntecedent[] getAntecedents(IProverSequent seq) {
    Predicate goal = seq.goal();
	
    Predicate P = null;
    Predicate Q = null;
    %match (Predicate goal) {

      /**
       * Deduction: 
       *           H, P |- Q
       *         -----------
       *          H |- P => Q
       */
      Limp(PP, QQ) -> {
        P = `PP;
        Q = `QQ;
      }

    }

    if (P == null)
      return null;
	
    // There will be 1 antecidents
    IAntecedent[] antecidents = new IAntecedent[1];

    // Added hypothesis P
    Set<Predicate> addedHyps = new HashSet<Predicate>(1);
    addedHyps.add(P);
    // Select the new hypothesis P
    IHypAction hypAction = ProverFactory.makeSelectHypAction(addedHyps);
    antecidents[0] = ProverFactory.makeAntecedent(Q, addedHyps, hypAction);

    return antecidents;
  }
	
}