ConstantTerm.java

package org.archstudio.prolog.term;

import static com.google.common.base.Preconditions.checkNotNull;

import java.util.Map;

import org.archstudio.prolog.engine.ProofContext;
import org.archstudio.prolog.op.Evaluable;

public class ConstantTerm extends AbstractTerm implements Term, Evaluable {

	private final Object value;

	public ConstantTerm(Object value) {
		this.value = checkNotNull(value);
	}

	@Override
	public Number evaluate(ProofContext proofContext, Map<VariableTerm, Term> variables) {
		if (value instanceof Number) {
			return (Number) value;
		}
		throw new RuntimeException("Not evaluable: " + this);
	}

	@Override
	public Term resolve(ProofContext proofContext, Map<VariableTerm, Term> variables) {
		return this;
	}

	@Override
	public String toString() {
		return value.toString();
	}

	public Object getValue() {
		return value;
	}

	@Override
	public int hashCode() {
		final int prime = 31;
		int result = 1;
		result = prime * result + (value == null ? 0 : value.hashCode());
		return result;
	}

	@Override
	public boolean equals(Object obj) {
		if (this == obj) {
			return true;
		}
		if (obj == null) {
			return false;
		}
		if (getClass() != obj.getClass()) {
			return false;
		}
		ConstantTerm other = (ConstantTerm) obj;
		if (value == null) {
			if (other.value != null) {
				return false;
			}
		}
		else if (!value.equals(other.value)) {
			return false;
		}
		return true;
	}
}