Asymptote A

Percentage Accurate: 77.2% → 99.9%
Time: 5.7s
Alternatives: 3
Speedup: 1.2×

Specification

?
\[\begin{array}{l} \\ \frac{1}{x + 1} - \frac{1}{x - 1} \end{array} \]
(FPCore (x) :precision binary64 (- (/ 1.0 (+ x 1.0)) (/ 1.0 (- x 1.0))))
double code(double x) {
	return (1.0 / (x + 1.0)) - (1.0 / (x - 1.0));
}
real(8) function code(x)
    real(8), intent (in) :: x
    code = (1.0d0 / (x + 1.0d0)) - (1.0d0 / (x - 1.0d0))
end function
public static double code(double x) {
	return (1.0 / (x + 1.0)) - (1.0 / (x - 1.0));
}
def code(x):
	return (1.0 / (x + 1.0)) - (1.0 / (x - 1.0))
function code(x)
	return Float64(Float64(1.0 / Float64(x + 1.0)) - Float64(1.0 / Float64(x - 1.0)))
end
function tmp = code(x)
	tmp = (1.0 / (x + 1.0)) - (1.0 / (x - 1.0));
end
code[x_] := N[(N[(1.0 / N[(x + 1.0), $MachinePrecision]), $MachinePrecision] - N[(1.0 / N[(x - 1.0), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]
\begin{array}{l}

\\
\frac{1}{x + 1} - \frac{1}{x - 1}
\end{array}

Sampling outcomes in binary64 precision:

Local Percentage Accuracy vs ?

The average percentage accuracy by input value. Horizontal axis shows value of an input variable; the variable is choosen in the title. Vertical axis is accuracy; higher is better. Red represent the original program, while blue represents Herbie's suggestion. These can be toggled with buttons below the plot. The line is an average while dots represent individual samples.

Accuracy vs Speed?

Herbie found 3 alternatives:

AlternativeAccuracySpeedup
The accuracy (vertical axis) and speed (horizontal axis) of each alternatives. Up and to the right is better. The red square shows the initial program, and each blue circle shows an alternative.The line shows the best available speed-accuracy tradeoffs.

Initial Program: 77.2% accurate, 1.0× speedup?

\[\begin{array}{l} \\ \frac{1}{x + 1} - \frac{1}{x - 1} \end{array} \]
(FPCore (x) :precision binary64 (- (/ 1.0 (+ x 1.0)) (/ 1.0 (- x 1.0))))
double code(double x) {
	return (1.0 / (x + 1.0)) - (1.0 / (x - 1.0));
}
real(8) function code(x)
    real(8), intent (in) :: x
    code = (1.0d0 / (x + 1.0d0)) - (1.0d0 / (x - 1.0d0))
end function
public static double code(double x) {
	return (1.0 / (x + 1.0)) - (1.0 / (x - 1.0));
}
def code(x):
	return (1.0 / (x + 1.0)) - (1.0 / (x - 1.0))
function code(x)
	return Float64(Float64(1.0 / Float64(x + 1.0)) - Float64(1.0 / Float64(x - 1.0)))
end
function tmp = code(x)
	tmp = (1.0 / (x + 1.0)) - (1.0 / (x - 1.0));
end
code[x_] := N[(N[(1.0 / N[(x + 1.0), $MachinePrecision]), $MachinePrecision] - N[(1.0 / N[(x - 1.0), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]
\begin{array}{l}

\\
\frac{1}{x + 1} - \frac{1}{x - 1}
\end{array}

Alternative 1: 99.9% accurate, 1.2× speedup?

\[\begin{array}{l} \\ \frac{\frac{2}{1 - x}}{1 + x} \end{array} \]
(FPCore (x) :precision binary64 (/ (/ 2.0 (- 1.0 x)) (+ 1.0 x)))
double code(double x) {
	return (2.0 / (1.0 - x)) / (1.0 + x);
}
real(8) function code(x)
    real(8), intent (in) :: x
    code = (2.0d0 / (1.0d0 - x)) / (1.0d0 + x)
end function
public static double code(double x) {
	return (2.0 / (1.0 - x)) / (1.0 + x);
}
def code(x):
	return (2.0 / (1.0 - x)) / (1.0 + x)
function code(x)
	return Float64(Float64(2.0 / Float64(1.0 - x)) / Float64(1.0 + x))
end
function tmp = code(x)
	tmp = (2.0 / (1.0 - x)) / (1.0 + x);
end
code[x_] := N[(N[(2.0 / N[(1.0 - x), $MachinePrecision]), $MachinePrecision] / N[(1.0 + x), $MachinePrecision]), $MachinePrecision]
\begin{array}{l}

\\
\frac{\frac{2}{1 - x}}{1 + x}
\end{array}
Derivation
  1. Initial program 78.6%

    \[\frac{1}{x + 1} - \frac{1}{x - 1} \]
  2. Step-by-step derivation
    1. sub-neg78.6%

      \[\leadsto \color{blue}{\frac{1}{x + 1} + \left(-\frac{1}{x - 1}\right)} \]
    2. +-commutative78.6%

      \[\leadsto \color{blue}{\left(-\frac{1}{x - 1}\right) + \frac{1}{x + 1}} \]
    3. neg-sub078.6%

      \[\leadsto \color{blue}{\left(0 - \frac{1}{x - 1}\right)} + \frac{1}{x + 1} \]
    4. associate-+l-78.6%

      \[\leadsto \color{blue}{0 - \left(\frac{1}{x - 1} - \frac{1}{x + 1}\right)} \]
    5. sub-neg78.6%

      \[\leadsto 0 - \color{blue}{\left(\frac{1}{x - 1} + \left(-\frac{1}{x + 1}\right)\right)} \]
    6. associate--r+78.6%

      \[\leadsto \color{blue}{\left(0 - \frac{1}{x - 1}\right) - \left(-\frac{1}{x + 1}\right)} \]
    7. neg-sub078.6%

      \[\leadsto \color{blue}{\left(-\frac{1}{x - 1}\right)} - \left(-\frac{1}{x + 1}\right) \]
    8. distribute-neg-frac78.6%

      \[\leadsto \color{blue}{\frac{-1}{x - 1}} - \left(-\frac{1}{x + 1}\right) \]
    9. metadata-eval78.6%

      \[\leadsto \frac{\color{blue}{-1}}{x - 1} - \left(-\frac{1}{x + 1}\right) \]
    10. metadata-eval78.6%

      \[\leadsto \frac{\color{blue}{\frac{1}{-1}}}{x - 1} - \left(-\frac{1}{x + 1}\right) \]
    11. metadata-eval78.6%

      \[\leadsto \frac{\frac{1}{\color{blue}{-1}}}{x - 1} - \left(-\frac{1}{x + 1}\right) \]
    12. associate-/r*78.6%

      \[\leadsto \color{blue}{\frac{1}{\left(-1\right) \cdot \left(x - 1\right)}} - \left(-\frac{1}{x + 1}\right) \]
    13. metadata-eval78.6%

      \[\leadsto \frac{1}{\color{blue}{-1} \cdot \left(x - 1\right)} - \left(-\frac{1}{x + 1}\right) \]
    14. neg-mul-178.6%

      \[\leadsto \frac{1}{\color{blue}{-\left(x - 1\right)}} - \left(-\frac{1}{x + 1}\right) \]
    15. sub0-neg78.6%

      \[\leadsto \frac{1}{\color{blue}{0 - \left(x - 1\right)}} - \left(-\frac{1}{x + 1}\right) \]
    16. associate-+l-78.6%

      \[\leadsto \frac{1}{\color{blue}{\left(0 - x\right) + 1}} - \left(-\frac{1}{x + 1}\right) \]
    17. neg-sub078.6%

      \[\leadsto \frac{1}{\color{blue}{\left(-x\right)} + 1} - \left(-\frac{1}{x + 1}\right) \]
    18. +-commutative78.6%

      \[\leadsto \frac{1}{\color{blue}{1 + \left(-x\right)}} - \left(-\frac{1}{x + 1}\right) \]
    19. unsub-neg78.6%

      \[\leadsto \frac{1}{\color{blue}{1 - x}} - \left(-\frac{1}{x + 1}\right) \]
    20. distribute-neg-frac78.6%

      \[\leadsto \frac{1}{1 - x} - \color{blue}{\frac{-1}{x + 1}} \]
    21. metadata-eval78.6%

      \[\leadsto \frac{1}{1 - x} - \frac{\color{blue}{-1}}{x + 1} \]
    22. metadata-eval78.6%

      \[\leadsto \frac{1}{1 - x} - \frac{\color{blue}{\frac{1}{-1}}}{x + 1} \]
    23. metadata-eval78.6%

      \[\leadsto \frac{1}{1 - x} - \frac{\frac{1}{\color{blue}{-1}}}{x + 1} \]
    24. associate-/r*78.6%

      \[\leadsto \frac{1}{1 - x} - \color{blue}{\frac{1}{\left(-1\right) \cdot \left(x + 1\right)}} \]
    25. metadata-eval78.6%

      \[\leadsto \frac{1}{1 - x} - \frac{1}{\color{blue}{-1} \cdot \left(x + 1\right)} \]
    26. neg-mul-178.6%

      \[\leadsto \frac{1}{1 - x} - \frac{1}{\color{blue}{-\left(x + 1\right)}} \]
  3. Simplified78.6%

    \[\leadsto \color{blue}{\frac{1}{1 - x} - \frac{1}{-1 - x}} \]
  4. Step-by-step derivation
    1. sub-neg78.6%

      \[\leadsto \color{blue}{\frac{1}{1 - x} + \left(-\frac{1}{-1 - x}\right)} \]
    2. distribute-neg-frac78.6%

      \[\leadsto \frac{1}{1 - x} + \color{blue}{\frac{-1}{-1 - x}} \]
    3. metadata-eval78.6%

      \[\leadsto \frac{1}{1 - x} + \frac{\color{blue}{-1}}{-1 - x} \]
  5. Applied egg-rr78.6%

    \[\leadsto \color{blue}{\frac{1}{1 - x} + \frac{-1}{-1 - x}} \]
  6. Simplified99.6%

    \[\leadsto \color{blue}{\frac{-2}{\left(1 - x\right) \cdot \left(-1 - x\right)}} \]
  7. Step-by-step derivation
    1. *-commutative99.6%

      \[\leadsto \frac{-2}{\color{blue}{\left(-1 - x\right) \cdot \left(1 - x\right)}} \]
    2. flip--99.6%

      \[\leadsto \frac{-2}{\color{blue}{\frac{-1 \cdot -1 - x \cdot x}{-1 + x}} \cdot \left(1 - x\right)} \]
    3. associate-*l/90.7%

      \[\leadsto \frac{-2}{\color{blue}{\frac{\left(-1 \cdot -1 - x \cdot x\right) \cdot \left(1 - x\right)}{-1 + x}}} \]
    4. metadata-eval90.7%

      \[\leadsto \frac{-2}{\frac{\left(\color{blue}{1} - x \cdot x\right) \cdot \left(1 - x\right)}{-1 + x}} \]
    5. pow290.7%

      \[\leadsto \frac{-2}{\frac{\left(1 - \color{blue}{{x}^{2}}\right) \cdot \left(1 - x\right)}{-1 + x}} \]
    6. +-commutative90.7%

      \[\leadsto \frac{-2}{\frac{\left(1 - {x}^{2}\right) \cdot \left(1 - x\right)}{\color{blue}{x + -1}}} \]
  8. Applied egg-rr90.7%

    \[\leadsto \frac{-2}{\color{blue}{\frac{\left(1 - {x}^{2}\right) \cdot \left(1 - x\right)}{x + -1}}} \]
  9. Step-by-step derivation
    1. associate-/r/90.6%

      \[\leadsto \color{blue}{\frac{-2}{\left(1 - {x}^{2}\right) \cdot \left(1 - x\right)} \cdot \left(x + -1\right)} \]
    2. *-commutative90.6%

      \[\leadsto \frac{-2}{\color{blue}{\left(1 - x\right) \cdot \left(1 - {x}^{2}\right)}} \cdot \left(x + -1\right) \]
    3. associate-/r*92.0%

      \[\leadsto \color{blue}{\frac{\frac{-2}{1 - x}}{1 - {x}^{2}}} \cdot \left(x + -1\right) \]
    4. metadata-eval92.0%

      \[\leadsto \frac{\frac{\color{blue}{-1 - 1}}{1 - x}}{1 - {x}^{2}} \cdot \left(x + -1\right) \]
    5. associate-/r/99.6%

      \[\leadsto \color{blue}{\frac{\frac{-1 - 1}{1 - x}}{\frac{1 - {x}^{2}}{x + -1}}} \]
    6. metadata-eval99.6%

      \[\leadsto \frac{\frac{-1 - 1}{1 - x}}{\frac{\color{blue}{-1 \cdot -1} - {x}^{2}}{x + -1}} \]
    7. unpow299.6%

      \[\leadsto \frac{\frac{-1 - 1}{1 - x}}{\frac{-1 \cdot -1 - \color{blue}{x \cdot x}}{x + -1}} \]
    8. +-commutative99.6%

      \[\leadsto \frac{\frac{-1 - 1}{1 - x}}{\frac{-1 \cdot -1 - x \cdot x}{\color{blue}{-1 + x}}} \]
    9. flip--99.9%

      \[\leadsto \frac{\frac{-1 - 1}{1 - x}}{\color{blue}{-1 - x}} \]
    10. frac-2neg99.9%

      \[\leadsto \color{blue}{\frac{-\frac{-1 - 1}{1 - x}}{-\left(-1 - x\right)}} \]
    11. div-inv99.8%

      \[\leadsto \color{blue}{\left(-\frac{-1 - 1}{1 - x}\right) \cdot \frac{1}{-\left(-1 - x\right)}} \]
    12. metadata-eval99.8%

      \[\leadsto \left(-\frac{\color{blue}{-2}}{1 - x}\right) \cdot \frac{1}{-\left(-1 - x\right)} \]
    13. distribute-neg-frac99.8%

      \[\leadsto \color{blue}{\frac{--2}{1 - x}} \cdot \frac{1}{-\left(-1 - x\right)} \]
    14. metadata-eval99.8%

      \[\leadsto \frac{\color{blue}{2}}{1 - x} \cdot \frac{1}{-\left(-1 - x\right)} \]
    15. sub-neg99.8%

      \[\leadsto \frac{2}{1 - x} \cdot \frac{1}{-\color{blue}{\left(-1 + \left(-x\right)\right)}} \]
    16. neg-mul-199.8%

      \[\leadsto \frac{2}{1 - x} \cdot \frac{1}{-\left(-1 + \color{blue}{-1 \cdot x}\right)} \]
    17. distribute-neg-in99.8%

      \[\leadsto \frac{2}{1 - x} \cdot \frac{1}{\color{blue}{\left(--1\right) + \left(--1 \cdot x\right)}} \]
    18. metadata-eval99.8%

      \[\leadsto \frac{2}{1 - x} \cdot \frac{1}{\color{blue}{1} + \left(--1 \cdot x\right)} \]
    19. *-commutative99.8%

      \[\leadsto \frac{2}{1 - x} \cdot \frac{1}{1 + \left(-\color{blue}{x \cdot -1}\right)} \]
  10. Applied egg-rr99.8%

    \[\leadsto \color{blue}{\frac{2}{1 - x} \cdot \frac{1}{1 - \left(-x\right)}} \]
  11. Step-by-step derivation
    1. associate-*r/99.9%

      \[\leadsto \color{blue}{\frac{\frac{2}{1 - x} \cdot 1}{1 - \left(-x\right)}} \]
    2. *-rgt-identity99.9%

      \[\leadsto \frac{\color{blue}{\frac{2}{1 - x}}}{1 - \left(-x\right)} \]
    3. sub-neg99.9%

      \[\leadsto \frac{\frac{2}{1 - x}}{\color{blue}{1 + \left(-\left(-x\right)\right)}} \]
    4. remove-double-neg99.9%

      \[\leadsto \frac{\frac{2}{1 - x}}{1 + \color{blue}{x}} \]
    5. +-commutative99.9%

      \[\leadsto \frac{\frac{2}{1 - x}}{\color{blue}{x + 1}} \]
  12. Simplified99.9%

    \[\leadsto \color{blue}{\frac{\frac{2}{1 - x}}{x + 1}} \]
  13. Final simplification99.9%

    \[\leadsto \frac{\frac{2}{1 - x}}{1 + x} \]

Alternative 2: 99.3% accurate, 1.2× speedup?

\[\begin{array}{l} \\ \frac{-2}{\left(1 - x\right) \cdot \left(-1 - x\right)} \end{array} \]
(FPCore (x) :precision binary64 (/ -2.0 (* (- 1.0 x) (- -1.0 x))))
double code(double x) {
	return -2.0 / ((1.0 - x) * (-1.0 - x));
}
real(8) function code(x)
    real(8), intent (in) :: x
    code = (-2.0d0) / ((1.0d0 - x) * ((-1.0d0) - x))
end function
public static double code(double x) {
	return -2.0 / ((1.0 - x) * (-1.0 - x));
}
def code(x):
	return -2.0 / ((1.0 - x) * (-1.0 - x))
function code(x)
	return Float64(-2.0 / Float64(Float64(1.0 - x) * Float64(-1.0 - x)))
end
function tmp = code(x)
	tmp = -2.0 / ((1.0 - x) * (-1.0 - x));
end
code[x_] := N[(-2.0 / N[(N[(1.0 - x), $MachinePrecision] * N[(-1.0 - x), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]
\begin{array}{l}

\\
\frac{-2}{\left(1 - x\right) \cdot \left(-1 - x\right)}
\end{array}
Derivation
  1. Initial program 78.6%

    \[\frac{1}{x + 1} - \frac{1}{x - 1} \]
  2. Step-by-step derivation
    1. sub-neg78.6%

      \[\leadsto \color{blue}{\frac{1}{x + 1} + \left(-\frac{1}{x - 1}\right)} \]
    2. +-commutative78.6%

      \[\leadsto \color{blue}{\left(-\frac{1}{x - 1}\right) + \frac{1}{x + 1}} \]
    3. neg-sub078.6%

      \[\leadsto \color{blue}{\left(0 - \frac{1}{x - 1}\right)} + \frac{1}{x + 1} \]
    4. associate-+l-78.6%

      \[\leadsto \color{blue}{0 - \left(\frac{1}{x - 1} - \frac{1}{x + 1}\right)} \]
    5. sub-neg78.6%

      \[\leadsto 0 - \color{blue}{\left(\frac{1}{x - 1} + \left(-\frac{1}{x + 1}\right)\right)} \]
    6. associate--r+78.6%

      \[\leadsto \color{blue}{\left(0 - \frac{1}{x - 1}\right) - \left(-\frac{1}{x + 1}\right)} \]
    7. neg-sub078.6%

      \[\leadsto \color{blue}{\left(-\frac{1}{x - 1}\right)} - \left(-\frac{1}{x + 1}\right) \]
    8. distribute-neg-frac78.6%

      \[\leadsto \color{blue}{\frac{-1}{x - 1}} - \left(-\frac{1}{x + 1}\right) \]
    9. metadata-eval78.6%

      \[\leadsto \frac{\color{blue}{-1}}{x - 1} - \left(-\frac{1}{x + 1}\right) \]
    10. metadata-eval78.6%

      \[\leadsto \frac{\color{blue}{\frac{1}{-1}}}{x - 1} - \left(-\frac{1}{x + 1}\right) \]
    11. metadata-eval78.6%

      \[\leadsto \frac{\frac{1}{\color{blue}{-1}}}{x - 1} - \left(-\frac{1}{x + 1}\right) \]
    12. associate-/r*78.6%

      \[\leadsto \color{blue}{\frac{1}{\left(-1\right) \cdot \left(x - 1\right)}} - \left(-\frac{1}{x + 1}\right) \]
    13. metadata-eval78.6%

      \[\leadsto \frac{1}{\color{blue}{-1} \cdot \left(x - 1\right)} - \left(-\frac{1}{x + 1}\right) \]
    14. neg-mul-178.6%

      \[\leadsto \frac{1}{\color{blue}{-\left(x - 1\right)}} - \left(-\frac{1}{x + 1}\right) \]
    15. sub0-neg78.6%

      \[\leadsto \frac{1}{\color{blue}{0 - \left(x - 1\right)}} - \left(-\frac{1}{x + 1}\right) \]
    16. associate-+l-78.6%

      \[\leadsto \frac{1}{\color{blue}{\left(0 - x\right) + 1}} - \left(-\frac{1}{x + 1}\right) \]
    17. neg-sub078.6%

      \[\leadsto \frac{1}{\color{blue}{\left(-x\right)} + 1} - \left(-\frac{1}{x + 1}\right) \]
    18. +-commutative78.6%

      \[\leadsto \frac{1}{\color{blue}{1 + \left(-x\right)}} - \left(-\frac{1}{x + 1}\right) \]
    19. unsub-neg78.6%

      \[\leadsto \frac{1}{\color{blue}{1 - x}} - \left(-\frac{1}{x + 1}\right) \]
    20. distribute-neg-frac78.6%

      \[\leadsto \frac{1}{1 - x} - \color{blue}{\frac{-1}{x + 1}} \]
    21. metadata-eval78.6%

      \[\leadsto \frac{1}{1 - x} - \frac{\color{blue}{-1}}{x + 1} \]
    22. metadata-eval78.6%

      \[\leadsto \frac{1}{1 - x} - \frac{\color{blue}{\frac{1}{-1}}}{x + 1} \]
    23. metadata-eval78.6%

      \[\leadsto \frac{1}{1 - x} - \frac{\frac{1}{\color{blue}{-1}}}{x + 1} \]
    24. associate-/r*78.6%

      \[\leadsto \frac{1}{1 - x} - \color{blue}{\frac{1}{\left(-1\right) \cdot \left(x + 1\right)}} \]
    25. metadata-eval78.6%

      \[\leadsto \frac{1}{1 - x} - \frac{1}{\color{blue}{-1} \cdot \left(x + 1\right)} \]
    26. neg-mul-178.6%

      \[\leadsto \frac{1}{1 - x} - \frac{1}{\color{blue}{-\left(x + 1\right)}} \]
  3. Simplified78.6%

    \[\leadsto \color{blue}{\frac{1}{1 - x} - \frac{1}{-1 - x}} \]
  4. Step-by-step derivation
    1. sub-neg78.6%

      \[\leadsto \color{blue}{\frac{1}{1 - x} + \left(-\frac{1}{-1 - x}\right)} \]
    2. distribute-neg-frac78.6%

      \[\leadsto \frac{1}{1 - x} + \color{blue}{\frac{-1}{-1 - x}} \]
    3. metadata-eval78.6%

      \[\leadsto \frac{1}{1 - x} + \frac{\color{blue}{-1}}{-1 - x} \]
  5. Applied egg-rr78.6%

    \[\leadsto \color{blue}{\frac{1}{1 - x} + \frac{-1}{-1 - x}} \]
  6. Simplified99.6%

    \[\leadsto \color{blue}{\frac{-2}{\left(1 - x\right) \cdot \left(-1 - x\right)}} \]
  7. Final simplification99.6%

    \[\leadsto \frac{-2}{\left(1 - x\right) \cdot \left(-1 - x\right)} \]

Alternative 3: 50.1% accurate, 11.0× speedup?

\[\begin{array}{l} \\ 2 \end{array} \]
(FPCore (x) :precision binary64 2.0)
double code(double x) {
	return 2.0;
}
real(8) function code(x)
    real(8), intent (in) :: x
    code = 2.0d0
end function
public static double code(double x) {
	return 2.0;
}
def code(x):
	return 2.0
function code(x)
	return 2.0
end
function tmp = code(x)
	tmp = 2.0;
end
code[x_] := 2.0
\begin{array}{l}

\\
2
\end{array}
Derivation
  1. Initial program 78.6%

    \[\frac{1}{x + 1} - \frac{1}{x - 1} \]
  2. Step-by-step derivation
    1. sub-neg78.6%

      \[\leadsto \color{blue}{\frac{1}{x + 1} + \left(-\frac{1}{x - 1}\right)} \]
    2. +-commutative78.6%

      \[\leadsto \color{blue}{\left(-\frac{1}{x - 1}\right) + \frac{1}{x + 1}} \]
    3. neg-sub078.6%

      \[\leadsto \color{blue}{\left(0 - \frac{1}{x - 1}\right)} + \frac{1}{x + 1} \]
    4. associate-+l-78.6%

      \[\leadsto \color{blue}{0 - \left(\frac{1}{x - 1} - \frac{1}{x + 1}\right)} \]
    5. sub-neg78.6%

      \[\leadsto 0 - \color{blue}{\left(\frac{1}{x - 1} + \left(-\frac{1}{x + 1}\right)\right)} \]
    6. associate--r+78.6%

      \[\leadsto \color{blue}{\left(0 - \frac{1}{x - 1}\right) - \left(-\frac{1}{x + 1}\right)} \]
    7. neg-sub078.6%

      \[\leadsto \color{blue}{\left(-\frac{1}{x - 1}\right)} - \left(-\frac{1}{x + 1}\right) \]
    8. distribute-neg-frac78.6%

      \[\leadsto \color{blue}{\frac{-1}{x - 1}} - \left(-\frac{1}{x + 1}\right) \]
    9. metadata-eval78.6%

      \[\leadsto \frac{\color{blue}{-1}}{x - 1} - \left(-\frac{1}{x + 1}\right) \]
    10. metadata-eval78.6%

      \[\leadsto \frac{\color{blue}{\frac{1}{-1}}}{x - 1} - \left(-\frac{1}{x + 1}\right) \]
    11. metadata-eval78.6%

      \[\leadsto \frac{\frac{1}{\color{blue}{-1}}}{x - 1} - \left(-\frac{1}{x + 1}\right) \]
    12. associate-/r*78.6%

      \[\leadsto \color{blue}{\frac{1}{\left(-1\right) \cdot \left(x - 1\right)}} - \left(-\frac{1}{x + 1}\right) \]
    13. metadata-eval78.6%

      \[\leadsto \frac{1}{\color{blue}{-1} \cdot \left(x - 1\right)} - \left(-\frac{1}{x + 1}\right) \]
    14. neg-mul-178.6%

      \[\leadsto \frac{1}{\color{blue}{-\left(x - 1\right)}} - \left(-\frac{1}{x + 1}\right) \]
    15. sub0-neg78.6%

      \[\leadsto \frac{1}{\color{blue}{0 - \left(x - 1\right)}} - \left(-\frac{1}{x + 1}\right) \]
    16. associate-+l-78.6%

      \[\leadsto \frac{1}{\color{blue}{\left(0 - x\right) + 1}} - \left(-\frac{1}{x + 1}\right) \]
    17. neg-sub078.6%

      \[\leadsto \frac{1}{\color{blue}{\left(-x\right)} + 1} - \left(-\frac{1}{x + 1}\right) \]
    18. +-commutative78.6%

      \[\leadsto \frac{1}{\color{blue}{1 + \left(-x\right)}} - \left(-\frac{1}{x + 1}\right) \]
    19. unsub-neg78.6%

      \[\leadsto \frac{1}{\color{blue}{1 - x}} - \left(-\frac{1}{x + 1}\right) \]
    20. distribute-neg-frac78.6%

      \[\leadsto \frac{1}{1 - x} - \color{blue}{\frac{-1}{x + 1}} \]
    21. metadata-eval78.6%

      \[\leadsto \frac{1}{1 - x} - \frac{\color{blue}{-1}}{x + 1} \]
    22. metadata-eval78.6%

      \[\leadsto \frac{1}{1 - x} - \frac{\color{blue}{\frac{1}{-1}}}{x + 1} \]
    23. metadata-eval78.6%

      \[\leadsto \frac{1}{1 - x} - \frac{\frac{1}{\color{blue}{-1}}}{x + 1} \]
    24. associate-/r*78.6%

      \[\leadsto \frac{1}{1 - x} - \color{blue}{\frac{1}{\left(-1\right) \cdot \left(x + 1\right)}} \]
    25. metadata-eval78.6%

      \[\leadsto \frac{1}{1 - x} - \frac{1}{\color{blue}{-1} \cdot \left(x + 1\right)} \]
    26. neg-mul-178.6%

      \[\leadsto \frac{1}{1 - x} - \frac{1}{\color{blue}{-\left(x + 1\right)}} \]
  3. Simplified78.6%

    \[\leadsto \color{blue}{\frac{1}{1 - x} - \frac{1}{-1 - x}} \]
  4. Taylor expanded in x around 0 48.4%

    \[\leadsto \color{blue}{2} \]
  5. Final simplification48.4%

    \[\leadsto 2 \]

Reproduce

?
herbie shell --seed 2023318 
(FPCore (x)
  :name "Asymptote A"
  :precision binary64
  (- (/ 1.0 (+ x 1.0)) (/ 1.0 (- x 1.0))))