Package dk.brics.string.stringoperations

Source Code of dk.brics.string.stringoperations.Prefix

package dk.brics.string.stringoperations;

import dk.brics.automaton.Automaton;
import dk.brics.automaton.State;
import dk.brics.automaton.StatePair;
import dk.brics.string.charset.CharSet;

import java.util.HashSet;
import java.util.Set;

/**
* Automaton operation for {@link StringBuffer#substring(0,int)}.
*/
public class Prefix extends UnaryOperation {

    /**
     * Constructs new operation object.
     */
    public Prefix() {
    }

    /**
     * Automaton operation.
     * Constructs new automaton as copy of <tt>a</tt> with a new accept state <i>s</i>.
     * Epsilon transitions are added from every state to <i>s</i>.
     *
     * @param a input automaton
     * @return resulting automaton
     */
    @Override
    public Automaton op(Automaton a) {
        Automaton b = a.clone();
        State accept = new State();
        accept.setAccept(true);
        Set<StatePair> epsilons = new HashSet<StatePair>();
        for (State s : b.getStates()) {
            epsilons.add(new StatePair(s, accept));
        }
        b.addEpsilons(epsilons);
        b.minimize();
        return b;
    }

    @Override
    public String toString() {
        return "prefix";
    }

    @Override
    public int getPriority() {
        return 4;
    }

    @Override
    public CharSet charsetTransfer(CharSet a) {
        return a;
    }

    @Override
    public int hashCode() {
        return getClass().hashCode();
    }

    @Override
    public boolean equals(Object obj) {
        return obj instanceof Prefix;
    }
}
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