(d: number)
| 168 | * h/2 for O(h⁴) truncation — high-order poles like x⁻¹⁰⁰ and degree-20 |
| 169 | * polynomial antiderivatives are far outside plain central-difference |
| 170 | * accuracy at REL_TOL. */ |
| 171 | function dF( |
| 172 | F: BoxedExpression, |
| 173 | x: string, |
| 174 | xv: number | C, |
| 175 | h: number |
| 176 | ): C | null { |
| 177 | const at = (d: number): C | null => |
| 178 | complexAt( |