```typescript
/** a divided by b. */
export function safeDivide(a: number, b: number): number {
  if (typeof a !== 'number' || typeof b !== 'number' || !isFinite(a) || !isFinite(b) ) {
    throw new Error('Both arguments must be finite numbers');
  } else if (b === 0 || b === -0) {
    throw new Error('Divisor cannot be zero or -zero');
  }
  return a / b;
}
```