```ts
/** a divided by b, with safety checks for division by zero and non-finite numbers. */
export function safeDivide(a: number, b: number): number {
  if (!isFinite(a) || !isFinite(b)) {
    throw new Error("Both arguments must be finite numbers.");
  }
  if (b === 0 || b === -0) {
    throw new Error("Division by zero is not allowed.");
  }
  return a / b;
}
```