\[\frac{-\left(f + n\right)}{f - n}\]
Test:
subtraction fraction
Bits:
128 bits
Bits error versus f
Bits error versus n
Time: 6.1 s
Input Error: 0.0
Output Error: 0.0
Log: ⚲
Profile: 🕒
\(\log \left(e^{\frac{1}{\frac{f - n}{-\left(f + n\right)}}}\right)\)
  1. Started with
    \[\frac{-\left(f + n\right)}{f - n}\]
    0.0
  2. Using strategy rm
    0.0
  3. Applied clear-num to get
    \[\color{red}{\frac{-\left(f + n\right)}{f - n}} \leadsto \color{blue}{\frac{1}{\frac{f - n}{-\left(f + n\right)}}}\]
    0.0
  4. Using strategy rm
    0.0
  5. Applied add-log-exp to get
    \[\color{red}{\frac{1}{\frac{f - n}{-\left(f + n\right)}}} \leadsto \color{blue}{\log \left(e^{\frac{1}{\frac{f - n}{-\left(f + n\right)}}}\right)}\]
    0.0

Original test:


(lambda ((f default) (n default))
  #:name "subtraction fraction"
  (/ (- (+ f n)) (- f n)))