adaptive-expressions/src/builtinFunctions/average.ts

Common Expression Language

/**
 * @module adaptive-expressions
 */
/**
 * Copyright (c) Microsoft Corporation. All rights reserved.
 * Licensed under the MIT License.
 */

import { EvaluateExpressionDelegate, ExpressionEvaluator } from '../expressionEvaluator';
import { ExpressionType } from '../expressionType';
import { FunctionUtils } from '../functionUtils';
import { ReturnType } from '../returnType';

/**
 * Return the average of a numeric array.
 */
export class Average extends ExpressionEvaluator {
    /**
     * Initializes a new instance of the [Average](xref:adaptive-expressions.Average) class.
     */
    constructor() {
        super(ExpressionType.Average, Average.evaluator(), ReturnType.Number, FunctionUtils.validateUnary);
    }

    /**
     * @private
     */
    private static evaluator(): EvaluateExpressionDelegate {
        return FunctionUtils.apply(
            (args: any[]): number => args[0].reduce((x: number, y: number): number => x + y) / args[0].length,
            FunctionUtils.verifyNumericList,
        );
    }
}