?

Average Accuracy: 47.0% → 87.1%
Time: 15.7s
Precision: binary64
Cost: 14216

?

\[\frac{\left(-b_2\right) - \sqrt{b_2 \cdot b_2 - a \cdot c}}{a} \]
\[\begin{array}{l} \mathbf{if}\;b_2 \leq -6 \cdot 10^{+34}:\\ \;\;\;\;\frac{-0.5 \cdot c}{b_2}\\ \mathbf{elif}\;b_2 \leq -7.4 \cdot 10^{-277}:\\ \;\;\;\;\frac{\frac{-1}{\frac{1}{\frac{c}{\frac{b_2 - \sqrt{\mathsf{fma}\left(b_2, b_2, c \cdot \left(-a\right)\right)}}{a}}}}}{a}\\ \mathbf{elif}\;b_2 \leq 4 \cdot 10^{+111}:\\ \;\;\;\;\frac{\left(-b_2\right) - \sqrt{b_2 \cdot b_2 - c \cdot a}}{a}\\ \mathbf{else}:\\ \;\;\;\;\frac{\left(\frac{c \cdot 0.5}{\frac{b_2}{a}} - b_2\right) - b_2}{a}\\ \end{array} \]
(FPCore (a b_2 c)
 :precision binary64
 (/ (- (- b_2) (sqrt (- (* b_2 b_2) (* a c)))) a))
(FPCore (a b_2 c)
 :precision binary64
 (if (<= b_2 -6e+34)
   (/ (* -0.5 c) b_2)
   (if (<= b_2 -7.4e-277)
     (/
      (/ -1.0 (/ 1.0 (/ c (/ (- b_2 (sqrt (fma b_2 b_2 (* c (- a))))) a))))
      a)
     (if (<= b_2 4e+111)
       (/ (- (- b_2) (sqrt (- (* b_2 b_2) (* c a)))) a)
       (/ (- (- (/ (* c 0.5) (/ b_2 a)) b_2) b_2) a)))))
double code(double a, double b_2, double c) {
	return (-b_2 - sqrt(((b_2 * b_2) - (a * c)))) / a;
}
double code(double a, double b_2, double c) {
	double tmp;
	if (b_2 <= -6e+34) {
		tmp = (-0.5 * c) / b_2;
	} else if (b_2 <= -7.4e-277) {
		tmp = (-1.0 / (1.0 / (c / ((b_2 - sqrt(fma(b_2, b_2, (c * -a)))) / a)))) / a;
	} else if (b_2 <= 4e+111) {
		tmp = (-b_2 - sqrt(((b_2 * b_2) - (c * a)))) / a;
	} else {
		tmp = ((((c * 0.5) / (b_2 / a)) - b_2) - b_2) / a;
	}
	return tmp;
}
function code(a, b_2, c)
	return Float64(Float64(Float64(-b_2) - sqrt(Float64(Float64(b_2 * b_2) - Float64(a * c)))) / a)
end
function code(a, b_2, c)
	tmp = 0.0
	if (b_2 <= -6e+34)
		tmp = Float64(Float64(-0.5 * c) / b_2);
	elseif (b_2 <= -7.4e-277)
		tmp = Float64(Float64(-1.0 / Float64(1.0 / Float64(c / Float64(Float64(b_2 - sqrt(fma(b_2, b_2, Float64(c * Float64(-a))))) / a)))) / a);
	elseif (b_2 <= 4e+111)
		tmp = Float64(Float64(Float64(-b_2) - sqrt(Float64(Float64(b_2 * b_2) - Float64(c * a)))) / a);
	else
		tmp = Float64(Float64(Float64(Float64(Float64(c * 0.5) / Float64(b_2 / a)) - b_2) - b_2) / a);
	end
	return tmp
end
code[a_, b$95$2_, c_] := N[(N[((-b$95$2) - N[Sqrt[N[(N[(b$95$2 * b$95$2), $MachinePrecision] - N[(a * c), $MachinePrecision]), $MachinePrecision]], $MachinePrecision]), $MachinePrecision] / a), $MachinePrecision]
code[a_, b$95$2_, c_] := If[LessEqual[b$95$2, -6e+34], N[(N[(-0.5 * c), $MachinePrecision] / b$95$2), $MachinePrecision], If[LessEqual[b$95$2, -7.4e-277], N[(N[(-1.0 / N[(1.0 / N[(c / N[(N[(b$95$2 - N[Sqrt[N[(b$95$2 * b$95$2 + N[(c * (-a)), $MachinePrecision]), $MachinePrecision]], $MachinePrecision]), $MachinePrecision] / a), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]), $MachinePrecision] / a), $MachinePrecision], If[LessEqual[b$95$2, 4e+111], N[(N[((-b$95$2) - N[Sqrt[N[(N[(b$95$2 * b$95$2), $MachinePrecision] - N[(c * a), $MachinePrecision]), $MachinePrecision]], $MachinePrecision]), $MachinePrecision] / a), $MachinePrecision], N[(N[(N[(N[(N[(c * 0.5), $MachinePrecision] / N[(b$95$2 / a), $MachinePrecision]), $MachinePrecision] - b$95$2), $MachinePrecision] - b$95$2), $MachinePrecision] / a), $MachinePrecision]]]]
\frac{\left(-b_2\right) - \sqrt{b_2 \cdot b_2 - a \cdot c}}{a}
\begin{array}{l}
\mathbf{if}\;b_2 \leq -6 \cdot 10^{+34}:\\
\;\;\;\;\frac{-0.5 \cdot c}{b_2}\\

\mathbf{elif}\;b_2 \leq -7.4 \cdot 10^{-277}:\\
\;\;\;\;\frac{\frac{-1}{\frac{1}{\frac{c}{\frac{b_2 - \sqrt{\mathsf{fma}\left(b_2, b_2, c \cdot \left(-a\right)\right)}}{a}}}}}{a}\\

\mathbf{elif}\;b_2 \leq 4 \cdot 10^{+111}:\\
\;\;\;\;\frac{\left(-b_2\right) - \sqrt{b_2 \cdot b_2 - c \cdot a}}{a}\\

\mathbf{else}:\\
\;\;\;\;\frac{\left(\frac{c \cdot 0.5}{\frac{b_2}{a}} - b_2\right) - b_2}{a}\\


\end{array}

Error?

Derivation?

  1. Split input into 4 regimes
  2. if b_2 < -6.00000000000000037e34

    1. Initial program 11.6%

      \[\frac{\left(-b_2\right) - \sqrt{b_2 \cdot b_2 - a \cdot c}}{a} \]
    2. Taylor expanded in b_2 around -inf 92.8%

      \[\leadsto \color{blue}{-0.5 \cdot \frac{c}{b_2}} \]
    3. Applied egg-rr92.9%

      \[\leadsto \color{blue}{\frac{-0.5 \cdot c}{b_2}} \]
      Proof

      [Start]92.8

      \[ -0.5 \cdot \frac{c}{b_2} \]

      associate-*r/ [=>]92.9

      \[ \color{blue}{\frac{-0.5 \cdot c}{b_2}} \]

    if -6.00000000000000037e34 < b_2 < -7.3999999999999997e-277

    1. Initial program 53.2%

      \[\frac{\left(-b_2\right) - \sqrt{b_2 \cdot b_2 - a \cdot c}}{a} \]
    2. Applied egg-rr52.2%

      \[\leadsto \frac{\color{blue}{\frac{\frac{-\left(a \cdot c + \left(b_2 \cdot b_2 - b_2 \cdot b_2\right)\right)}{a \cdot c + \left(b_2 \cdot b_2 - b_2 \cdot b_2\right)}}{\frac{1}{b_2 + \sqrt{b_2 \cdot b_2 - a \cdot c}}}}}{a} \]
      Proof

      [Start]53.2

      \[ \frac{\left(-b_2\right) - \sqrt{b_2 \cdot b_2 - a \cdot c}}{a} \]

      flip-- [=>]53.1

      \[ \frac{\color{blue}{\frac{\left(-b_2\right) \cdot \left(-b_2\right) - \sqrt{b_2 \cdot b_2 - a \cdot c} \cdot \sqrt{b_2 \cdot b_2 - a \cdot c}}{\left(-b_2\right) + \sqrt{b_2 \cdot b_2 - a \cdot c}}}}{a} \]

      frac-2neg [=>]53.1

      \[ \frac{\color{blue}{\frac{-\left(\left(-b_2\right) \cdot \left(-b_2\right) - \sqrt{b_2 \cdot b_2 - a \cdot c} \cdot \sqrt{b_2 \cdot b_2 - a \cdot c}\right)}{-\left(\left(-b_2\right) + \sqrt{b_2 \cdot b_2 - a \cdot c}\right)}}}{a} \]

      add-sqr-sqrt [=>]53.1

      \[ \frac{\frac{-\left(\left(-b_2\right) \cdot \left(-b_2\right) - \sqrt{b_2 \cdot b_2 - a \cdot c} \cdot \sqrt{b_2 \cdot b_2 - a \cdot c}\right)}{-\left(\color{blue}{\sqrt{-b_2} \cdot \sqrt{-b_2}} + \sqrt{b_2 \cdot b_2 - a \cdot c}\right)}}{a} \]

      sqrt-unprod [=>]53.0

      \[ \frac{\frac{-\left(\left(-b_2\right) \cdot \left(-b_2\right) - \sqrt{b_2 \cdot b_2 - a \cdot c} \cdot \sqrt{b_2 \cdot b_2 - a \cdot c}\right)}{-\left(\color{blue}{\sqrt{\left(-b_2\right) \cdot \left(-b_2\right)}} + \sqrt{b_2 \cdot b_2 - a \cdot c}\right)}}{a} \]

      sqr-neg [=>]53.0

      \[ \frac{\frac{-\left(\left(-b_2\right) \cdot \left(-b_2\right) - \sqrt{b_2 \cdot b_2 - a \cdot c} \cdot \sqrt{b_2 \cdot b_2 - a \cdot c}\right)}{-\left(\sqrt{\color{blue}{b_2 \cdot b_2}} + \sqrt{b_2 \cdot b_2 - a \cdot c}\right)}}{a} \]

      sqrt-prod [=>]0.0

      \[ \frac{\frac{-\left(\left(-b_2\right) \cdot \left(-b_2\right) - \sqrt{b_2 \cdot b_2 - a \cdot c} \cdot \sqrt{b_2 \cdot b_2 - a \cdot c}\right)}{-\left(\color{blue}{\sqrt{b_2} \cdot \sqrt{b_2}} + \sqrt{b_2 \cdot b_2 - a \cdot c}\right)}}{a} \]

      add-sqr-sqrt [<=]49.4

      \[ \frac{\frac{-\left(\left(-b_2\right) \cdot \left(-b_2\right) - \sqrt{b_2 \cdot b_2 - a \cdot c} \cdot \sqrt{b_2 \cdot b_2 - a \cdot c}\right)}{-\left(\color{blue}{b_2} + \sqrt{b_2 \cdot b_2 - a \cdot c}\right)}}{a} \]

      distribute-neg-out [<=]49.4

      \[ \frac{\frac{-\left(\left(-b_2\right) \cdot \left(-b_2\right) - \sqrt{b_2 \cdot b_2 - a \cdot c} \cdot \sqrt{b_2 \cdot b_2 - a \cdot c}\right)}{\color{blue}{\left(-b_2\right) + \left(-\sqrt{b_2 \cdot b_2 - a \cdot c}\right)}}}{a} \]

      sub-neg [<=]49.4

      \[ \frac{\frac{-\left(\left(-b_2\right) \cdot \left(-b_2\right) - \sqrt{b_2 \cdot b_2 - a \cdot c} \cdot \sqrt{b_2 \cdot b_2 - a \cdot c}\right)}{\color{blue}{\left(-b_2\right) - \sqrt{b_2 \cdot b_2 - a \cdot c}}}}{a} \]

      flip-- [=>]49.3

      \[ \frac{\frac{-\left(\left(-b_2\right) \cdot \left(-b_2\right) - \sqrt{b_2 \cdot b_2 - a \cdot c} \cdot \sqrt{b_2 \cdot b_2 - a \cdot c}\right)}{\color{blue}{\frac{\left(-b_2\right) \cdot \left(-b_2\right) - \sqrt{b_2 \cdot b_2 - a \cdot c} \cdot \sqrt{b_2 \cdot b_2 - a \cdot c}}{\left(-b_2\right) + \sqrt{b_2 \cdot b_2 - a \cdot c}}}}}{a} \]

      div-inv [=>]49.2

      \[ \frac{\frac{-\left(\left(-b_2\right) \cdot \left(-b_2\right) - \sqrt{b_2 \cdot b_2 - a \cdot c} \cdot \sqrt{b_2 \cdot b_2 - a \cdot c}\right)}{\color{blue}{\left(\left(-b_2\right) \cdot \left(-b_2\right) - \sqrt{b_2 \cdot b_2 - a \cdot c} \cdot \sqrt{b_2 \cdot b_2 - a \cdot c}\right) \cdot \frac{1}{\left(-b_2\right) + \sqrt{b_2 \cdot b_2 - a \cdot c}}}}}{a} \]
    3. Taylor expanded in a around 0 53.1%

      \[\leadsto \frac{\frac{\color{blue}{-1}}{\frac{1}{b_2 + \sqrt{b_2 \cdot b_2 - a \cdot c}}}}{a} \]
    4. Applied egg-rr73.3%

      \[\leadsto \frac{\frac{-1}{\frac{1}{\color{blue}{\left(a \cdot c + \left(b_2 \cdot b_2 - b_2 \cdot b_2\right)\right) \cdot \frac{1}{b_2 - \sqrt{b_2 \cdot b_2 - a \cdot c}}}}}}{a} \]
      Proof

      [Start]53.1

      \[ \frac{\frac{-1}{\frac{1}{b_2 + \sqrt{b_2 \cdot b_2 - a \cdot c}}}}{a} \]

      flip-+ [=>]53.1

      \[ \frac{\frac{-1}{\frac{1}{\color{blue}{\frac{b_2 \cdot b_2 - \sqrt{b_2 \cdot b_2 - a \cdot c} \cdot \sqrt{b_2 \cdot b_2 - a \cdot c}}{b_2 - \sqrt{b_2 \cdot b_2 - a \cdot c}}}}}}{a} \]

      div-inv [=>]53.0

      \[ \frac{\frac{-1}{\frac{1}{\color{blue}{\left(b_2 \cdot b_2 - \sqrt{b_2 \cdot b_2 - a \cdot c} \cdot \sqrt{b_2 \cdot b_2 - a \cdot c}\right) \cdot \frac{1}{b_2 - \sqrt{b_2 \cdot b_2 - a \cdot c}}}}}}{a} \]

      add-sqr-sqrt [<=]53.0

      \[ \frac{\frac{-1}{\frac{1}{\left(b_2 \cdot b_2 - \color{blue}{\left(b_2 \cdot b_2 - a \cdot c\right)}\right) \cdot \frac{1}{b_2 - \sqrt{b_2 \cdot b_2 - a \cdot c}}}}}{a} \]

      associate--r- [=>]73.3

      \[ \frac{\frac{-1}{\frac{1}{\color{blue}{\left(\left(b_2 \cdot b_2 - b_2 \cdot b_2\right) + a \cdot c\right)} \cdot \frac{1}{b_2 - \sqrt{b_2 \cdot b_2 - a \cdot c}}}}}{a} \]

      +-commutative [=>]73.3

      \[ \frac{\frac{-1}{\frac{1}{\color{blue}{\left(a \cdot c + \left(b_2 \cdot b_2 - b_2 \cdot b_2\right)\right)} \cdot \frac{1}{b_2 - \sqrt{b_2 \cdot b_2 - a \cdot c}}}}}{a} \]
    5. Simplified77.6%

      \[\leadsto \frac{\frac{-1}{\frac{1}{\color{blue}{\frac{c}{\frac{b_2 - \sqrt{\mathsf{fma}\left(b_2, b_2, c \cdot \left(-a\right)\right)}}{a}}}}}}{a} \]
      Proof

      [Start]73.3

      \[ \frac{\frac{-1}{\frac{1}{\left(a \cdot c + \left(b_2 \cdot b_2 - b_2 \cdot b_2\right)\right) \cdot \frac{1}{b_2 - \sqrt{b_2 \cdot b_2 - a \cdot c}}}}}{a} \]

      associate-*r/ [=>]73.3

      \[ \frac{\frac{-1}{\frac{1}{\color{blue}{\frac{\left(a \cdot c + \left(b_2 \cdot b_2 - b_2 \cdot b_2\right)\right) \cdot 1}{b_2 - \sqrt{b_2 \cdot b_2 - a \cdot c}}}}}}{a} \]

      *-rgt-identity [=>]73.3

      \[ \frac{\frac{-1}{\frac{1}{\frac{\color{blue}{a \cdot c + \left(b_2 \cdot b_2 - b_2 \cdot b_2\right)}}{b_2 - \sqrt{b_2 \cdot b_2 - a \cdot c}}}}}{a} \]

      +-commutative [=>]73.3

      \[ \frac{\frac{-1}{\frac{1}{\frac{\color{blue}{\left(b_2 \cdot b_2 - b_2 \cdot b_2\right) + a \cdot c}}{b_2 - \sqrt{b_2 \cdot b_2 - a \cdot c}}}}}{a} \]

      +-inverses [=>]73.3

      \[ \frac{\frac{-1}{\frac{1}{\frac{\color{blue}{0} + a \cdot c}{b_2 - \sqrt{b_2 \cdot b_2 - a \cdot c}}}}}{a} \]

      +-lft-identity [=>]73.3

      \[ \frac{\frac{-1}{\frac{1}{\frac{\color{blue}{a \cdot c}}{b_2 - \sqrt{b_2 \cdot b_2 - a \cdot c}}}}}{a} \]

      *-commutative [=>]73.3

      \[ \frac{\frac{-1}{\frac{1}{\frac{\color{blue}{c \cdot a}}{b_2 - \sqrt{b_2 \cdot b_2 - a \cdot c}}}}}{a} \]

      associate-/l* [=>]77.6

      \[ \frac{\frac{-1}{\frac{1}{\color{blue}{\frac{c}{\frac{b_2 - \sqrt{b_2 \cdot b_2 - a \cdot c}}{a}}}}}}{a} \]

      fma-neg [=>]77.6

      \[ \frac{\frac{-1}{\frac{1}{\frac{c}{\frac{b_2 - \sqrt{\color{blue}{\mathsf{fma}\left(b_2, b_2, -a \cdot c\right)}}}{a}}}}}{a} \]

      distribute-lft-neg-in [=>]77.6

      \[ \frac{\frac{-1}{\frac{1}{\frac{c}{\frac{b_2 - \sqrt{\mathsf{fma}\left(b_2, b_2, \color{blue}{\left(-a\right) \cdot c}\right)}}{a}}}}}{a} \]

      *-commutative [=>]77.6

      \[ \frac{\frac{-1}{\frac{1}{\frac{c}{\frac{b_2 - \sqrt{\mathsf{fma}\left(b_2, b_2, \color{blue}{c \cdot \left(-a\right)}\right)}}{a}}}}}{a} \]

    if -7.3999999999999997e-277 < b_2 < 3.99999999999999983e111

    1. Initial program 85.5%

      \[\frac{\left(-b_2\right) - \sqrt{b_2 \cdot b_2 - a \cdot c}}{a} \]

    if 3.99999999999999983e111 < b_2

    1. Initial program 22.7%

      \[\frac{\left(-b_2\right) - \sqrt{b_2 \cdot b_2 - a \cdot c}}{a} \]
    2. Taylor expanded in b_2 around inf 82.7%

      \[\leadsto \frac{\left(-b_2\right) - \color{blue}{\left(b_2 + -0.5 \cdot \frac{c \cdot a}{b_2}\right)}}{a} \]
    3. Simplified93.4%

      \[\leadsto \frac{\left(-b_2\right) - \color{blue}{\left(b_2 + \frac{c \cdot -0.5}{\frac{b_2}{a}}\right)}}{a} \]
      Proof

      [Start]82.7

      \[ \frac{\left(-b_2\right) - \left(b_2 + -0.5 \cdot \frac{c \cdot a}{b_2}\right)}{a} \]

      associate-/l* [=>]93.4

      \[ \frac{\left(-b_2\right) - \left(b_2 + -0.5 \cdot \color{blue}{\frac{c}{\frac{b_2}{a}}}\right)}{a} \]

      associate-*r/ [=>]93.4

      \[ \frac{\left(-b_2\right) - \left(b_2 + \color{blue}{\frac{-0.5 \cdot c}{\frac{b_2}{a}}}\right)}{a} \]

      *-commutative [=>]93.4

      \[ \frac{\left(-b_2\right) - \left(b_2 + \frac{\color{blue}{c \cdot -0.5}}{\frac{b_2}{a}}\right)}{a} \]
  3. Recombined 4 regimes into one program.
  4. Final simplification87.1%

    \[\leadsto \begin{array}{l} \mathbf{if}\;b_2 \leq -6 \cdot 10^{+34}:\\ \;\;\;\;\frac{-0.5 \cdot c}{b_2}\\ \mathbf{elif}\;b_2 \leq -7.4 \cdot 10^{-277}:\\ \;\;\;\;\frac{\frac{-1}{\frac{1}{\frac{c}{\frac{b_2 - \sqrt{\mathsf{fma}\left(b_2, b_2, c \cdot \left(-a\right)\right)}}{a}}}}}{a}\\ \mathbf{elif}\;b_2 \leq 4 \cdot 10^{+111}:\\ \;\;\;\;\frac{\left(-b_2\right) - \sqrt{b_2 \cdot b_2 - c \cdot a}}{a}\\ \mathbf{else}:\\ \;\;\;\;\frac{\left(\frac{c \cdot 0.5}{\frac{b_2}{a}} - b_2\right) - b_2}{a}\\ \end{array} \]

Alternatives

Alternative 1
Accuracy83.9%
Cost7432
\[\begin{array}{l} \mathbf{if}\;b_2 \leq -1.8 \cdot 10^{-106}:\\ \;\;\;\;\frac{-0.5 \cdot c}{b_2}\\ \mathbf{elif}\;b_2 \leq 10^{+112}:\\ \;\;\;\;\frac{\left(-b_2\right) - \sqrt{b_2 \cdot b_2 - c \cdot a}}{a}\\ \mathbf{else}:\\ \;\;\;\;\frac{\left(\frac{c \cdot 0.5}{\frac{b_2}{a}} - b_2\right) - b_2}{a}\\ \end{array} \]
Alternative 2
Accuracy78.6%
Cost7240
\[\begin{array}{l} \mathbf{if}\;b_2 \leq -1.8 \cdot 10^{-106}:\\ \;\;\;\;\frac{-0.5 \cdot c}{b_2}\\ \mathbf{elif}\;b_2 \leq 10^{-79}:\\ \;\;\;\;\frac{\left(-b_2\right) - \sqrt{c \cdot \left(-a\right)}}{a}\\ \mathbf{else}:\\ \;\;\;\;\frac{b_2}{a} \cdot -2 + 0.5 \cdot \frac{c}{b_2}\\ \end{array} \]
Alternative 3
Accuracy64.5%
Cost836
\[\begin{array}{l} \mathbf{if}\;b_2 \leq -5 \cdot 10^{-310}:\\ \;\;\;\;\frac{-0.5 \cdot c}{b_2}\\ \mathbf{else}:\\ \;\;\;\;\frac{b_2}{a} \cdot -2 + 0.5 \cdot \frac{c}{b_2}\\ \end{array} \]
Alternative 4
Accuracy42.7%
Cost452
\[\begin{array}{l} \mathbf{if}\;b_2 \leq -7 \cdot 10^{-277}:\\ \;\;\;\;-0.5 \cdot \frac{c}{b_2}\\ \mathbf{else}:\\ \;\;\;\;\frac{-b_2}{a}\\ \end{array} \]
Alternative 5
Accuracy42.7%
Cost452
\[\begin{array}{l} \mathbf{if}\;b_2 \leq -5.8 \cdot 10^{-277}:\\ \;\;\;\;\frac{-0.5 \cdot c}{b_2}\\ \mathbf{else}:\\ \;\;\;\;\frac{-b_2}{a}\\ \end{array} \]
Alternative 6
Accuracy64.5%
Cost452
\[\begin{array}{l} \mathbf{if}\;b_2 \leq -1.8 \cdot 10^{-277}:\\ \;\;\;\;\frac{-0.5 \cdot c}{b_2}\\ \mathbf{else}:\\ \;\;\;\;\frac{b_2 \cdot -2}{a}\\ \end{array} \]
Alternative 7
Accuracy7.5%
Cost256
\[\frac{-b_2}{a} \]

Error

Reproduce?

herbie shell --seed 2023131 
(FPCore (a b_2 c)
  :name "quad2m (problem 3.2.1, negative)"
  :precision binary64
  (/ (- (- b_2) (sqrt (- (* b_2 b_2) (* a c)))) a))