
(FPCore (x y z) :precision binary64 (/ (- (+ (* x x) (* y y)) (* z z)) (* y 2.0)))
double code(double x, double y, double z) {
return (((x * x) + (y * y)) - (z * z)) / (y * 2.0);
}
real(8) function code(x, y, z)
real(8), intent (in) :: x
real(8), intent (in) :: y
real(8), intent (in) :: z
code = (((x * x) + (y * y)) - (z * z)) / (y * 2.0d0)
end function
public static double code(double x, double y, double z) {
return (((x * x) + (y * y)) - (z * z)) / (y * 2.0);
}
def code(x, y, z): return (((x * x) + (y * y)) - (z * z)) / (y * 2.0)
function code(x, y, z) return Float64(Float64(Float64(Float64(x * x) + Float64(y * y)) - Float64(z * z)) / Float64(y * 2.0)) end
function tmp = code(x, y, z) tmp = (((x * x) + (y * y)) - (z * z)) / (y * 2.0); end
code[x_, y_, z_] := N[(N[(N[(N[(x * x), $MachinePrecision] + N[(y * y), $MachinePrecision]), $MachinePrecision] - N[(z * z), $MachinePrecision]), $MachinePrecision] / N[(y * 2.0), $MachinePrecision]), $MachinePrecision]
\begin{array}{l}
\\
\frac{\left(x \cdot x + y \cdot y\right) - z \cdot z}{y \cdot 2}
\end{array}
Sampling outcomes in binary64 precision:
Herbie found 7 alternatives:
| Alternative | Accuracy | Speedup |
|---|
(FPCore (x y z) :precision binary64 (/ (- (+ (* x x) (* y y)) (* z z)) (* y 2.0)))
double code(double x, double y, double z) {
return (((x * x) + (y * y)) - (z * z)) / (y * 2.0);
}
real(8) function code(x, y, z)
real(8), intent (in) :: x
real(8), intent (in) :: y
real(8), intent (in) :: z
code = (((x * x) + (y * y)) - (z * z)) / (y * 2.0d0)
end function
public static double code(double x, double y, double z) {
return (((x * x) + (y * y)) - (z * z)) / (y * 2.0);
}
def code(x, y, z): return (((x * x) + (y * y)) - (z * z)) / (y * 2.0)
function code(x, y, z) return Float64(Float64(Float64(Float64(x * x) + Float64(y * y)) - Float64(z * z)) / Float64(y * 2.0)) end
function tmp = code(x, y, z) tmp = (((x * x) + (y * y)) - (z * z)) / (y * 2.0); end
code[x_, y_, z_] := N[(N[(N[(N[(x * x), $MachinePrecision] + N[(y * y), $MachinePrecision]), $MachinePrecision] - N[(z * z), $MachinePrecision]), $MachinePrecision] / N[(y * 2.0), $MachinePrecision]), $MachinePrecision]
\begin{array}{l}
\\
\frac{\left(x \cdot x + y \cdot y\right) - z \cdot z}{y \cdot 2}
\end{array}
(FPCore (x y z) :precision binary64 (* 0.5 (fma (+ z x) (/ (- x z) y) y)))
double code(double x, double y, double z) {
return 0.5 * fma((z + x), ((x - z) / y), y);
}
function code(x, y, z) return Float64(0.5 * fma(Float64(z + x), Float64(Float64(x - z) / y), y)) end
code[x_, y_, z_] := N[(0.5 * N[(N[(z + x), $MachinePrecision] * N[(N[(x - z), $MachinePrecision] / y), $MachinePrecision] + y), $MachinePrecision]), $MachinePrecision]
\begin{array}{l}
\\
0.5 \cdot \mathsf{fma}\left(z + x, \frac{x - z}{y}, y\right)
\end{array}
Initial program 68.4%
Taylor expanded in x around 0
distribute-lft-outN/A
*-commutativeN/A
lower-*.f64N/A
Applied rewrites99.9%
Final simplification99.9%
(FPCore (x y z)
:precision binary64
(let* ((t_0 (/ (- (+ (* y y) (* x x)) (* z z)) (* 2.0 y))))
(if (<= t_0 0.0)
(* (/ (* -0.5 z) y) z)
(if (<= t_0 5e+148) (* 0.5 y) (* (* (/ x y) x) 0.5)))))
double code(double x, double y, double z) {
double t_0 = (((y * y) + (x * x)) - (z * z)) / (2.0 * y);
double tmp;
if (t_0 <= 0.0) {
tmp = ((-0.5 * z) / y) * z;
} else if (t_0 <= 5e+148) {
tmp = 0.5 * y;
} else {
tmp = ((x / y) * x) * 0.5;
}
return tmp;
}
real(8) function code(x, y, z)
real(8), intent (in) :: x
real(8), intent (in) :: y
real(8), intent (in) :: z
real(8) :: t_0
real(8) :: tmp
t_0 = (((y * y) + (x * x)) - (z * z)) / (2.0d0 * y)
if (t_0 <= 0.0d0) then
tmp = (((-0.5d0) * z) / y) * z
else if (t_0 <= 5d+148) then
tmp = 0.5d0 * y
else
tmp = ((x / y) * x) * 0.5d0
end if
code = tmp
end function
public static double code(double x, double y, double z) {
double t_0 = (((y * y) + (x * x)) - (z * z)) / (2.0 * y);
double tmp;
if (t_0 <= 0.0) {
tmp = ((-0.5 * z) / y) * z;
} else if (t_0 <= 5e+148) {
tmp = 0.5 * y;
} else {
tmp = ((x / y) * x) * 0.5;
}
return tmp;
}
def code(x, y, z): t_0 = (((y * y) + (x * x)) - (z * z)) / (2.0 * y) tmp = 0 if t_0 <= 0.0: tmp = ((-0.5 * z) / y) * z elif t_0 <= 5e+148: tmp = 0.5 * y else: tmp = ((x / y) * x) * 0.5 return tmp
function code(x, y, z) t_0 = Float64(Float64(Float64(Float64(y * y) + Float64(x * x)) - Float64(z * z)) / Float64(2.0 * y)) tmp = 0.0 if (t_0 <= 0.0) tmp = Float64(Float64(Float64(-0.5 * z) / y) * z); elseif (t_0 <= 5e+148) tmp = Float64(0.5 * y); else tmp = Float64(Float64(Float64(x / y) * x) * 0.5); end return tmp end
function tmp_2 = code(x, y, z) t_0 = (((y * y) + (x * x)) - (z * z)) / (2.0 * y); tmp = 0.0; if (t_0 <= 0.0) tmp = ((-0.5 * z) / y) * z; elseif (t_0 <= 5e+148) tmp = 0.5 * y; else tmp = ((x / y) * x) * 0.5; end tmp_2 = tmp; end
code[x_, y_, z_] := Block[{t$95$0 = N[(N[(N[(N[(y * y), $MachinePrecision] + N[(x * x), $MachinePrecision]), $MachinePrecision] - N[(z * z), $MachinePrecision]), $MachinePrecision] / N[(2.0 * y), $MachinePrecision]), $MachinePrecision]}, If[LessEqual[t$95$0, 0.0], N[(N[(N[(-0.5 * z), $MachinePrecision] / y), $MachinePrecision] * z), $MachinePrecision], If[LessEqual[t$95$0, 5e+148], N[(0.5 * y), $MachinePrecision], N[(N[(N[(x / y), $MachinePrecision] * x), $MachinePrecision] * 0.5), $MachinePrecision]]]]
\begin{array}{l}
\\
\begin{array}{l}
t_0 := \frac{\left(y \cdot y + x \cdot x\right) - z \cdot z}{2 \cdot y}\\
\mathbf{if}\;t\_0 \leq 0:\\
\;\;\;\;\frac{-0.5 \cdot z}{y} \cdot z\\
\mathbf{elif}\;t\_0 \leq 5 \cdot 10^{+148}:\\
\;\;\;\;0.5 \cdot y\\
\mathbf{else}:\\
\;\;\;\;\left(\frac{x}{y} \cdot x\right) \cdot 0.5\\
\end{array}
\end{array}
if (/.f64 (-.f64 (+.f64 (*.f64 x x) (*.f64 y y)) (*.f64 z z)) (*.f64 y #s(literal 2 binary64))) < 0.0Initial program 71.2%
Taylor expanded in x around 0
distribute-lft-outN/A
*-commutativeN/A
lower-*.f64N/A
Applied rewrites99.9%
Taylor expanded in z around inf
Applied rewrites29.6%
Applied rewrites29.6%
if 0.0 < (/.f64 (-.f64 (+.f64 (*.f64 x x) (*.f64 y y)) (*.f64 z z)) (*.f64 y #s(literal 2 binary64))) < 5.00000000000000024e148Initial program 99.9%
Taylor expanded in y around inf
lower-*.f6468.1
Applied rewrites68.1%
if 5.00000000000000024e148 < (/.f64 (-.f64 (+.f64 (*.f64 x x) (*.f64 y y)) (*.f64 z z)) (*.f64 y #s(literal 2 binary64))) Initial program 59.8%
Taylor expanded in x around inf
*-commutativeN/A
lower-*.f64N/A
lower-/.f64N/A
unpow2N/A
lower-*.f6441.8
Applied rewrites41.8%
Applied rewrites45.9%
Final simplification40.4%
(FPCore (x y z) :precision binary64 (if (<= (/ (- (+ (* y y) (* x x)) (* z z)) (* 2.0 y)) 0.0) (* (fma (- z) (/ z y) y) 0.5) (* (fma (/ x y) x y) 0.5)))
double code(double x, double y, double z) {
double tmp;
if (((((y * y) + (x * x)) - (z * z)) / (2.0 * y)) <= 0.0) {
tmp = fma(-z, (z / y), y) * 0.5;
} else {
tmp = fma((x / y), x, y) * 0.5;
}
return tmp;
}
function code(x, y, z) tmp = 0.0 if (Float64(Float64(Float64(Float64(y * y) + Float64(x * x)) - Float64(z * z)) / Float64(2.0 * y)) <= 0.0) tmp = Float64(fma(Float64(-z), Float64(z / y), y) * 0.5); else tmp = Float64(fma(Float64(x / y), x, y) * 0.5); end return tmp end
code[x_, y_, z_] := If[LessEqual[N[(N[(N[(N[(y * y), $MachinePrecision] + N[(x * x), $MachinePrecision]), $MachinePrecision] - N[(z * z), $MachinePrecision]), $MachinePrecision] / N[(2.0 * y), $MachinePrecision]), $MachinePrecision], 0.0], N[(N[((-z) * N[(z / y), $MachinePrecision] + y), $MachinePrecision] * 0.5), $MachinePrecision], N[(N[(N[(x / y), $MachinePrecision] * x + y), $MachinePrecision] * 0.5), $MachinePrecision]]
\begin{array}{l}
\\
\begin{array}{l}
\mathbf{if}\;\frac{\left(y \cdot y + x \cdot x\right) - z \cdot z}{2 \cdot y} \leq 0:\\
\;\;\;\;\mathsf{fma}\left(-z, \frac{z}{y}, y\right) \cdot 0.5\\
\mathbf{else}:\\
\;\;\;\;\mathsf{fma}\left(\frac{x}{y}, x, y\right) \cdot 0.5\\
\end{array}
\end{array}
if (/.f64 (-.f64 (+.f64 (*.f64 x x) (*.f64 y y)) (*.f64 z z)) (*.f64 y #s(literal 2 binary64))) < 0.0Initial program 71.2%
Taylor expanded in x around 0
*-commutativeN/A
div-subN/A
unpow2N/A
associate-/l*N/A
*-inversesN/A
*-rgt-identityN/A
lower-*.f64N/A
lower--.f64N/A
lower-/.f64N/A
unpow2N/A
lower-*.f6464.8
Applied rewrites64.8%
Applied rewrites68.8%
if 0.0 < (/.f64 (-.f64 (+.f64 (*.f64 x x) (*.f64 y y)) (*.f64 z z)) (*.f64 y #s(literal 2 binary64))) Initial program 66.1%
Taylor expanded in z around 0
*-commutativeN/A
lower-*.f64N/A
div-addN/A
unpow2N/A
associate-/l*N/A
*-inversesN/A
*-rgt-identityN/A
unpow2N/A
associate-/l*N/A
*-commutativeN/A
lower-fma.f64N/A
lower-/.f6472.8
Applied rewrites72.8%
Final simplification70.9%
(FPCore (x y z) :precision binary64 (if (<= (/ (- (+ (* y y) (* x x)) (* z z)) (* 2.0 y)) 0.0) (* (/ (* -0.5 z) y) z) (* (fma (/ x y) x y) 0.5)))
double code(double x, double y, double z) {
double tmp;
if (((((y * y) + (x * x)) - (z * z)) / (2.0 * y)) <= 0.0) {
tmp = ((-0.5 * z) / y) * z;
} else {
tmp = fma((x / y), x, y) * 0.5;
}
return tmp;
}
function code(x, y, z) tmp = 0.0 if (Float64(Float64(Float64(Float64(y * y) + Float64(x * x)) - Float64(z * z)) / Float64(2.0 * y)) <= 0.0) tmp = Float64(Float64(Float64(-0.5 * z) / y) * z); else tmp = Float64(fma(Float64(x / y), x, y) * 0.5); end return tmp end
code[x_, y_, z_] := If[LessEqual[N[(N[(N[(N[(y * y), $MachinePrecision] + N[(x * x), $MachinePrecision]), $MachinePrecision] - N[(z * z), $MachinePrecision]), $MachinePrecision] / N[(2.0 * y), $MachinePrecision]), $MachinePrecision], 0.0], N[(N[(N[(-0.5 * z), $MachinePrecision] / y), $MachinePrecision] * z), $MachinePrecision], N[(N[(N[(x / y), $MachinePrecision] * x + y), $MachinePrecision] * 0.5), $MachinePrecision]]
\begin{array}{l}
\\
\begin{array}{l}
\mathbf{if}\;\frac{\left(y \cdot y + x \cdot x\right) - z \cdot z}{2 \cdot y} \leq 0:\\
\;\;\;\;\frac{-0.5 \cdot z}{y} \cdot z\\
\mathbf{else}:\\
\;\;\;\;\mathsf{fma}\left(\frac{x}{y}, x, y\right) \cdot 0.5\\
\end{array}
\end{array}
if (/.f64 (-.f64 (+.f64 (*.f64 x x) (*.f64 y y)) (*.f64 z z)) (*.f64 y #s(literal 2 binary64))) < 0.0Initial program 71.2%
Taylor expanded in x around 0
distribute-lft-outN/A
*-commutativeN/A
lower-*.f64N/A
Applied rewrites99.9%
Taylor expanded in z around inf
Applied rewrites29.6%
Applied rewrites29.6%
if 0.0 < (/.f64 (-.f64 (+.f64 (*.f64 x x) (*.f64 y y)) (*.f64 z z)) (*.f64 y #s(literal 2 binary64))) Initial program 66.1%
Taylor expanded in z around 0
*-commutativeN/A
lower-*.f64N/A
div-addN/A
unpow2N/A
associate-/l*N/A
*-inversesN/A
*-rgt-identityN/A
unpow2N/A
associate-/l*N/A
*-commutativeN/A
lower-fma.f64N/A
lower-/.f6472.8
Applied rewrites72.8%
Final simplification53.0%
(FPCore (x y z) :precision binary64 (if (<= (/ (- (+ (* y y) (* x x)) (* z z)) (* 2.0 y)) 0.0) (* (/ (* -0.5 z) y) z) (* 0.5 y)))
double code(double x, double y, double z) {
double tmp;
if (((((y * y) + (x * x)) - (z * z)) / (2.0 * y)) <= 0.0) {
tmp = ((-0.5 * z) / y) * z;
} else {
tmp = 0.5 * y;
}
return tmp;
}
real(8) function code(x, y, z)
real(8), intent (in) :: x
real(8), intent (in) :: y
real(8), intent (in) :: z
real(8) :: tmp
if (((((y * y) + (x * x)) - (z * z)) / (2.0d0 * y)) <= 0.0d0) then
tmp = (((-0.5d0) * z) / y) * z
else
tmp = 0.5d0 * y
end if
code = tmp
end function
public static double code(double x, double y, double z) {
double tmp;
if (((((y * y) + (x * x)) - (z * z)) / (2.0 * y)) <= 0.0) {
tmp = ((-0.5 * z) / y) * z;
} else {
tmp = 0.5 * y;
}
return tmp;
}
def code(x, y, z): tmp = 0 if ((((y * y) + (x * x)) - (z * z)) / (2.0 * y)) <= 0.0: tmp = ((-0.5 * z) / y) * z else: tmp = 0.5 * y return tmp
function code(x, y, z) tmp = 0.0 if (Float64(Float64(Float64(Float64(y * y) + Float64(x * x)) - Float64(z * z)) / Float64(2.0 * y)) <= 0.0) tmp = Float64(Float64(Float64(-0.5 * z) / y) * z); else tmp = Float64(0.5 * y); end return tmp end
function tmp_2 = code(x, y, z) tmp = 0.0; if (((((y * y) + (x * x)) - (z * z)) / (2.0 * y)) <= 0.0) tmp = ((-0.5 * z) / y) * z; else tmp = 0.5 * y; end tmp_2 = tmp; end
code[x_, y_, z_] := If[LessEqual[N[(N[(N[(N[(y * y), $MachinePrecision] + N[(x * x), $MachinePrecision]), $MachinePrecision] - N[(z * z), $MachinePrecision]), $MachinePrecision] / N[(2.0 * y), $MachinePrecision]), $MachinePrecision], 0.0], N[(N[(N[(-0.5 * z), $MachinePrecision] / y), $MachinePrecision] * z), $MachinePrecision], N[(0.5 * y), $MachinePrecision]]
\begin{array}{l}
\\
\begin{array}{l}
\mathbf{if}\;\frac{\left(y \cdot y + x \cdot x\right) - z \cdot z}{2 \cdot y} \leq 0:\\
\;\;\;\;\frac{-0.5 \cdot z}{y} \cdot z\\
\mathbf{else}:\\
\;\;\;\;0.5 \cdot y\\
\end{array}
\end{array}
if (/.f64 (-.f64 (+.f64 (*.f64 x x) (*.f64 y y)) (*.f64 z z)) (*.f64 y #s(literal 2 binary64))) < 0.0Initial program 71.2%
Taylor expanded in x around 0
distribute-lft-outN/A
*-commutativeN/A
lower-*.f64N/A
Applied rewrites99.9%
Taylor expanded in z around inf
Applied rewrites29.6%
Applied rewrites29.6%
if 0.0 < (/.f64 (-.f64 (+.f64 (*.f64 x x) (*.f64 y y)) (*.f64 z z)) (*.f64 y #s(literal 2 binary64))) Initial program 66.1%
Taylor expanded in y around inf
lower-*.f6433.0
Applied rewrites33.0%
Final simplification31.5%
(FPCore (x y z) :precision binary64 (if (<= (/ (- (+ (* y y) (* x x)) (* z z)) (* 2.0 y)) 0.0) (* (* (/ -0.5 y) z) z) (* 0.5 y)))
double code(double x, double y, double z) {
double tmp;
if (((((y * y) + (x * x)) - (z * z)) / (2.0 * y)) <= 0.0) {
tmp = ((-0.5 / y) * z) * z;
} else {
tmp = 0.5 * y;
}
return tmp;
}
real(8) function code(x, y, z)
real(8), intent (in) :: x
real(8), intent (in) :: y
real(8), intent (in) :: z
real(8) :: tmp
if (((((y * y) + (x * x)) - (z * z)) / (2.0d0 * y)) <= 0.0d0) then
tmp = (((-0.5d0) / y) * z) * z
else
tmp = 0.5d0 * y
end if
code = tmp
end function
public static double code(double x, double y, double z) {
double tmp;
if (((((y * y) + (x * x)) - (z * z)) / (2.0 * y)) <= 0.0) {
tmp = ((-0.5 / y) * z) * z;
} else {
tmp = 0.5 * y;
}
return tmp;
}
def code(x, y, z): tmp = 0 if ((((y * y) + (x * x)) - (z * z)) / (2.0 * y)) <= 0.0: tmp = ((-0.5 / y) * z) * z else: tmp = 0.5 * y return tmp
function code(x, y, z) tmp = 0.0 if (Float64(Float64(Float64(Float64(y * y) + Float64(x * x)) - Float64(z * z)) / Float64(2.0 * y)) <= 0.0) tmp = Float64(Float64(Float64(-0.5 / y) * z) * z); else tmp = Float64(0.5 * y); end return tmp end
function tmp_2 = code(x, y, z) tmp = 0.0; if (((((y * y) + (x * x)) - (z * z)) / (2.0 * y)) <= 0.0) tmp = ((-0.5 / y) * z) * z; else tmp = 0.5 * y; end tmp_2 = tmp; end
code[x_, y_, z_] := If[LessEqual[N[(N[(N[(N[(y * y), $MachinePrecision] + N[(x * x), $MachinePrecision]), $MachinePrecision] - N[(z * z), $MachinePrecision]), $MachinePrecision] / N[(2.0 * y), $MachinePrecision]), $MachinePrecision], 0.0], N[(N[(N[(-0.5 / y), $MachinePrecision] * z), $MachinePrecision] * z), $MachinePrecision], N[(0.5 * y), $MachinePrecision]]
\begin{array}{l}
\\
\begin{array}{l}
\mathbf{if}\;\frac{\left(y \cdot y + x \cdot x\right) - z \cdot z}{2 \cdot y} \leq 0:\\
\;\;\;\;\left(\frac{-0.5}{y} \cdot z\right) \cdot z\\
\mathbf{else}:\\
\;\;\;\;0.5 \cdot y\\
\end{array}
\end{array}
if (/.f64 (-.f64 (+.f64 (*.f64 x x) (*.f64 y y)) (*.f64 z z)) (*.f64 y #s(literal 2 binary64))) < 0.0Initial program 71.2%
Taylor expanded in x around 0
distribute-lft-outN/A
*-commutativeN/A
lower-*.f64N/A
Applied rewrites99.9%
Taylor expanded in z around inf
Applied rewrites29.6%
if 0.0 < (/.f64 (-.f64 (+.f64 (*.f64 x x) (*.f64 y y)) (*.f64 z z)) (*.f64 y #s(literal 2 binary64))) Initial program 66.1%
Taylor expanded in y around inf
lower-*.f6433.0
Applied rewrites33.0%
Final simplification31.5%
(FPCore (x y z) :precision binary64 (* 0.5 y))
double code(double x, double y, double z) {
return 0.5 * y;
}
real(8) function code(x, y, z)
real(8), intent (in) :: x
real(8), intent (in) :: y
real(8), intent (in) :: z
code = 0.5d0 * y
end function
public static double code(double x, double y, double z) {
return 0.5 * y;
}
def code(x, y, z): return 0.5 * y
function code(x, y, z) return Float64(0.5 * y) end
function tmp = code(x, y, z) tmp = 0.5 * y; end
code[x_, y_, z_] := N[(0.5 * y), $MachinePrecision]
\begin{array}{l}
\\
0.5 \cdot y
\end{array}
Initial program 68.4%
Taylor expanded in y around inf
lower-*.f6436.4
Applied rewrites36.4%
(FPCore (x y z) :precision binary64 (- (* y 0.5) (* (* (/ 0.5 y) (+ z x)) (- z x))))
double code(double x, double y, double z) {
return (y * 0.5) - (((0.5 / y) * (z + x)) * (z - x));
}
real(8) function code(x, y, z)
real(8), intent (in) :: x
real(8), intent (in) :: y
real(8), intent (in) :: z
code = (y * 0.5d0) - (((0.5d0 / y) * (z + x)) * (z - x))
end function
public static double code(double x, double y, double z) {
return (y * 0.5) - (((0.5 / y) * (z + x)) * (z - x));
}
def code(x, y, z): return (y * 0.5) - (((0.5 / y) * (z + x)) * (z - x))
function code(x, y, z) return Float64(Float64(y * 0.5) - Float64(Float64(Float64(0.5 / y) * Float64(z + x)) * Float64(z - x))) end
function tmp = code(x, y, z) tmp = (y * 0.5) - (((0.5 / y) * (z + x)) * (z - x)); end
code[x_, y_, z_] := N[(N[(y * 0.5), $MachinePrecision] - N[(N[(N[(0.5 / y), $MachinePrecision] * N[(z + x), $MachinePrecision]), $MachinePrecision] * N[(z - x), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]
\begin{array}{l}
\\
y \cdot 0.5 - \left(\frac{0.5}{y} \cdot \left(z + x\right)\right) \cdot \left(z - x\right)
\end{array}
herbie shell --seed 2024298
(FPCore (x y z)
:name "Diagrams.TwoD.Apollonian:initialConfig from diagrams-contrib-1.3.0.5, A"
:precision binary64
:alt
(! :herbie-platform default (- (* y 1/2) (* (* (/ 1/2 y) (+ z x)) (- z x))))
(/ (- (+ (* x x) (* y y)) (* z z)) (* y 2.0)))