```ts
{ function assertNumber(value: number): void {
    if (typeof value !== "number" || !Number.isFinite(value)) {
        throw new Error("value must be a finite number");
    }
} }

type C = [number, any?];

export function celsiusToFahrenheit(celsius: number): number {
    assertNumber(celsius);
    if (celsius < -273.15) {
        throw new Error("celsius must be at or above absolute zero");
    }
    return celsius * 1.8 + 32;
}

export function celsiusToKelvin(celsius: number): number {
    assertNumber(celsius);
    if (celsius < -273.15) {
        throw new Error("celsius must be at or above absolute zero");
    }
    return celsius + 273.15;
}
```