package models.algebra; import java.io.Serializable; import java.util.HashMap; public abstract class Expression implements Cloneable, Serializable { public abstract Expression getSubTerm(Position pos); /** * Get the unification between this expression and another expression. * @param another another expression * @return unified expression */ public abstract Expression unify(Expression another); /** * Get the inverse map to obtain a sub-term of a given output value back from the output value itself. * @param outputValue an output value (usually a term) * @param targetPos a position in outputValue * @return inverse map */ public abstract Expression getInverseMap(Expression outputValue, Position targetPos); public abstract boolean contains(Expression exp); public abstract Object clone(); public abstract <T extends Expression> HashMap<Position, T> getSubTerms(Class<T> clazz); public HashMap<Position, Variable> getVariables() { return getSubTerms(Variable.class); } /** * Get the implementation of this expression. * @param sideEffects an array with an optional implementation that should be written before the evaluation of this expression * @return the implementation to represent the value of this expression */ public String toImplementation(String[] sideEffects) { return toString(); } }