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sum.ts
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sum.ts
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import { TerminalStage } from '../../stages';
class SumCollector<IN extends number> extends TerminalStage<IN, number> {
private _sum = 0;
override consume(element: IN): void {
this._throwErrorIfNotNumber(element);
this._sum += element;
}
private _throwErrorIfNotNumber(value: unknown) {
if (typeof value !== 'number') {
throw new Error(
`[sum() collector] Numbers expected, erroneous pipeline element received was ${JSON.stringify(value)}`
);
}
}
override get(): number {
return this._sum;
}
override resume(): void {
this._sum = 0;
}
}
/**
* Return a terminal stage that calculates the sum of all elements in this pipeline. It assumes that every element
* is numeric, otherwise, it will throw an error when at least one element is not numeric.
*
* @template IN The type parameter of each incoming element in the pipeline.
*
* @returns
*/
export function sum<IN extends number>(): TerminalStage<IN, number> {
return new SumCollector<IN>();
}