Error

Derivation

1. Initial program 0.0

   \[\frac{-\left(f + n\right)}{f - n}\]
2. Using strategy rm

3. Applied add-log-exp0.0

   \[\leadsto \color{blue}{\log \left(e^{\frac{-\left(f + n\right)}{f - n}}\right)}\]
4. Using strategy rm

5. Applied expm1-log1p-u0.0

   \[\leadsto \log \color{blue}{\left((e^{\log_* (1 + e^{\frac{-\left(f + n\right)}{f - n}})} - 1)^*\right)}\]

6. Final simplification0.0

   \[\leadsto \log \left((e^{\log_* (1 + e^{\frac{-\left(n + f\right)}{f - n}})} - 1)^*\right)\]

Reproduce

herbie shell --seed 2019090 +o rules:numerics
(FPCore (f n)
  :name "subtraction fraction"
  (/ (- (+ f n)) (- f n)))