/**
 * @module adaptive-expressions
 */
/**
 * Copyright (c) Microsoft Corporation. All rights reserved.
 * Licensed under the MIT License.
 */
import { ExpressionEvaluator } from '../expressionEvaluator';
/**
 * Return true if a given input is a string.
 */
export declare class IsString extends ExpressionEvaluator {
    /**
     * Initializes a new instance of the [IsString](xref:adaptive-expressions.IsString) class.
     */
    constructor();
    /**
     * @private
     */
    private static evaluator;
}
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