src/main/java/org/apache/sling/scripting/sightly/compiler/expression/nodes/UnaryOperator.java

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 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
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 *
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package org.apache.sling.scripting.sightly.compiler.expression.nodes;

import org.apache.commons.lang3.StringUtils;
import org.apache.sling.scripting.sightly.compiler.util.ObjectModel;

/**
 * Unary operators used in expressions.
 */
public enum UnaryOperator {

    /** Evaluates to logical negation of the operand */
    NOT {
        @Override
        public Object eval(Object operand) {
            return !ObjectModel.toBoolean(operand);
        }
    },

    /** Evaluates whether the operand is a string of only whitespace characters */
    IS_WHITESPACE  {
        @Override
        public Object eval(Object operand) {
            return StringUtils.isWhitespace(ObjectModel.toString(operand));
        }
    },

    /**
     * Evaluates the length of a collection
     */
    LENGTH {
        @Override
        public Object eval(Object operand) {
            return ObjectModel.toCollection(operand).size();
        }
    };

    public abstract Object eval(Object operand);

}