Function unionExtentStartFromNumber

src/util/model.ts:1237–1241

(extent: number[], val: number | NullUndefined)

 *  - `extent` should be initialized as `initExtentForUnion()`.
 */
export function unionExtentStartFromNumber(extent: number[], val: number | NullUndefined): void {
    if (isValidNumberForExtent(val) && val < extent[0]) {
        extent[0] = val;
    }
}

/**
 * NOTICE: