
(FPCore (x y z t a) :precision binary64 (+ x (/ (* y (- z t)) (- a t))))
double code(double x, double y, double z, double t, double a) {
return x + ((y * (z - t)) / (a - t));
}
real(8) function code(x, y, z, t, a)
real(8), intent (in) :: x
real(8), intent (in) :: y
real(8), intent (in) :: z
real(8), intent (in) :: t
real(8), intent (in) :: a
code = x + ((y * (z - t)) / (a - t))
end function
public static double code(double x, double y, double z, double t, double a) {
return x + ((y * (z - t)) / (a - t));
}
def code(x, y, z, t, a): return x + ((y * (z - t)) / (a - t))
function code(x, y, z, t, a) return Float64(x + Float64(Float64(y * Float64(z - t)) / Float64(a - t))) end
function tmp = code(x, y, z, t, a) tmp = x + ((y * (z - t)) / (a - t)); end
code[x_, y_, z_, t_, a_] := N[(x + N[(N[(y * N[(z - t), $MachinePrecision]), $MachinePrecision] / N[(a - t), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]
\begin{array}{l}
\\
x + \frac{y \cdot \left(z - t\right)}{a - t}
\end{array}
Sampling outcomes in binary64 precision:
Herbie found 9 alternatives:
| Alternative | Accuracy | Speedup |
|---|
(FPCore (x y z t a) :precision binary64 (+ x (/ (* y (- z t)) (- a t))))
double code(double x, double y, double z, double t, double a) {
return x + ((y * (z - t)) / (a - t));
}
real(8) function code(x, y, z, t, a)
real(8), intent (in) :: x
real(8), intent (in) :: y
real(8), intent (in) :: z
real(8), intent (in) :: t
real(8), intent (in) :: a
code = x + ((y * (z - t)) / (a - t))
end function
public static double code(double x, double y, double z, double t, double a) {
return x + ((y * (z - t)) / (a - t));
}
def code(x, y, z, t, a): return x + ((y * (z - t)) / (a - t))
function code(x, y, z, t, a) return Float64(x + Float64(Float64(y * Float64(z - t)) / Float64(a - t))) end
function tmp = code(x, y, z, t, a) tmp = x + ((y * (z - t)) / (a - t)); end
code[x_, y_, z_, t_, a_] := N[(x + N[(N[(y * N[(z - t), $MachinePrecision]), $MachinePrecision] / N[(a - t), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]
\begin{array}{l}
\\
x + \frac{y \cdot \left(z - t\right)}{a - t}
\end{array}
(FPCore (x y z t a) :precision binary64 (fma (/ (- z t) (- a t)) y x))
double code(double x, double y, double z, double t, double a) {
return fma(((z - t) / (a - t)), y, x);
}
function code(x, y, z, t, a) return fma(Float64(Float64(z - t) / Float64(a - t)), y, x) end
code[x_, y_, z_, t_, a_] := N[(N[(N[(z - t), $MachinePrecision] / N[(a - t), $MachinePrecision]), $MachinePrecision] * y + x), $MachinePrecision]
\begin{array}{l}
\\
\mathsf{fma}\left(\frac{z - t}{a - t}, y, x\right)
\end{array}
Initial program 84.3%
lift-+.f64N/A
+-commutativeN/A
lift-/.f64N/A
lift-*.f64N/A
associate-/l*N/A
*-commutativeN/A
lower-fma.f64N/A
lower-/.f6498.8
Applied rewrites98.8%
(FPCore (x y z t a)
:precision binary64
(if (<= t -1.02e+93)
(+ x y)
(if (<= t 8.2e-72)
(fma (/ z a) y x)
(if (<= t 2.25e+157) (fma (/ (- z) t) y x) (+ x y)))))
double code(double x, double y, double z, double t, double a) {
double tmp;
if (t <= -1.02e+93) {
tmp = x + y;
} else if (t <= 8.2e-72) {
tmp = fma((z / a), y, x);
} else if (t <= 2.25e+157) {
tmp = fma((-z / t), y, x);
} else {
tmp = x + y;
}
return tmp;
}
function code(x, y, z, t, a) tmp = 0.0 if (t <= -1.02e+93) tmp = Float64(x + y); elseif (t <= 8.2e-72) tmp = fma(Float64(z / a), y, x); elseif (t <= 2.25e+157) tmp = fma(Float64(Float64(-z) / t), y, x); else tmp = Float64(x + y); end return tmp end
code[x_, y_, z_, t_, a_] := If[LessEqual[t, -1.02e+93], N[(x + y), $MachinePrecision], If[LessEqual[t, 8.2e-72], N[(N[(z / a), $MachinePrecision] * y + x), $MachinePrecision], If[LessEqual[t, 2.25e+157], N[(N[((-z) / t), $MachinePrecision] * y + x), $MachinePrecision], N[(x + y), $MachinePrecision]]]]
\begin{array}{l}
\\
\begin{array}{l}
\mathbf{if}\;t \leq -1.02 \cdot 10^{+93}:\\
\;\;\;\;x + y\\
\mathbf{elif}\;t \leq 8.2 \cdot 10^{-72}:\\
\;\;\;\;\mathsf{fma}\left(\frac{z}{a}, y, x\right)\\
\mathbf{elif}\;t \leq 2.25 \cdot 10^{+157}:\\
\;\;\;\;\mathsf{fma}\left(\frac{-z}{t}, y, x\right)\\
\mathbf{else}:\\
\;\;\;\;x + y\\
\end{array}
\end{array}
if t < -1.0200000000000001e93 or 2.24999999999999992e157 < t Initial program 64.8%
Taylor expanded in t around inf
+-commutativeN/A
lower-+.f6490.8
Applied rewrites90.8%
if -1.0200000000000001e93 < t < 8.20000000000000007e-72Initial program 94.2%
Taylor expanded in t around 0
+-commutativeN/A
associate-/l*N/A
*-commutativeN/A
lower-fma.f64N/A
lower-/.f6479.8
Applied rewrites79.8%
if 8.20000000000000007e-72 < t < 2.24999999999999992e157Initial program 97.8%
Taylor expanded in a around 0
+-commutativeN/A
mul-1-negN/A
associate-/l*N/A
*-commutativeN/A
distribute-lft-neg-inN/A
lower-fma.f64N/A
neg-sub0N/A
div-subN/A
*-inversesN/A
associate-+l-N/A
neg-sub0N/A
mul-1-negN/A
+-commutativeN/A
mul-1-negN/A
unsub-negN/A
lower--.f64N/A
lower-/.f6485.0
Applied rewrites85.0%
Taylor expanded in t around 0
Applied rewrites81.0%
Final simplification84.0%
(FPCore (x y z t a)
:precision binary64
(if (<= t -1.02e+93)
(+ x y)
(if (<= t 5.5e-9)
(fma (/ z a) y x)
(if (<= t 7.2e+65) (fma (- y) (/ z t) y) (+ x y)))))
double code(double x, double y, double z, double t, double a) {
double tmp;
if (t <= -1.02e+93) {
tmp = x + y;
} else if (t <= 5.5e-9) {
tmp = fma((z / a), y, x);
} else if (t <= 7.2e+65) {
tmp = fma(-y, (z / t), y);
} else {
tmp = x + y;
}
return tmp;
}
function code(x, y, z, t, a) tmp = 0.0 if (t <= -1.02e+93) tmp = Float64(x + y); elseif (t <= 5.5e-9) tmp = fma(Float64(z / a), y, x); elseif (t <= 7.2e+65) tmp = fma(Float64(-y), Float64(z / t), y); else tmp = Float64(x + y); end return tmp end
code[x_, y_, z_, t_, a_] := If[LessEqual[t, -1.02e+93], N[(x + y), $MachinePrecision], If[LessEqual[t, 5.5e-9], N[(N[(z / a), $MachinePrecision] * y + x), $MachinePrecision], If[LessEqual[t, 7.2e+65], N[((-y) * N[(z / t), $MachinePrecision] + y), $MachinePrecision], N[(x + y), $MachinePrecision]]]]
\begin{array}{l}
\\
\begin{array}{l}
\mathbf{if}\;t \leq -1.02 \cdot 10^{+93}:\\
\;\;\;\;x + y\\
\mathbf{elif}\;t \leq 5.5 \cdot 10^{-9}:\\
\;\;\;\;\mathsf{fma}\left(\frac{z}{a}, y, x\right)\\
\mathbf{elif}\;t \leq 7.2 \cdot 10^{+65}:\\
\;\;\;\;\mathsf{fma}\left(-y, \frac{z}{t}, y\right)\\
\mathbf{else}:\\
\;\;\;\;x + y\\
\end{array}
\end{array}
if t < -1.0200000000000001e93 or 7.19999999999999957e65 < t Initial program 70.2%
Taylor expanded in t around inf
+-commutativeN/A
lower-+.f6488.2
Applied rewrites88.2%
if -1.0200000000000001e93 < t < 5.4999999999999996e-9Initial program 94.7%
Taylor expanded in t around 0
+-commutativeN/A
associate-/l*N/A
*-commutativeN/A
lower-fma.f64N/A
lower-/.f6476.6
Applied rewrites76.6%
if 5.4999999999999996e-9 < t < 7.19999999999999957e65Initial program 99.7%
Taylor expanded in a around 0
+-commutativeN/A
mul-1-negN/A
associate-/l*N/A
*-commutativeN/A
distribute-lft-neg-inN/A
lower-fma.f64N/A
neg-sub0N/A
div-subN/A
*-inversesN/A
associate-+l-N/A
neg-sub0N/A
mul-1-negN/A
+-commutativeN/A
mul-1-negN/A
unsub-negN/A
lower--.f64N/A
lower-/.f6475.9
Applied rewrites75.9%
Taylor expanded in y around inf
Applied rewrites64.0%
Final simplification80.9%
(FPCore (x y z t a) :precision binary64 (let* ((t_1 (fma (- 1.0 (/ z t)) y x))) (if (<= t -6e-47) t_1 (if (<= t 4.2e-72) (fma (/ (- z t) a) y x) t_1))))
double code(double x, double y, double z, double t, double a) {
double t_1 = fma((1.0 - (z / t)), y, x);
double tmp;
if (t <= -6e-47) {
tmp = t_1;
} else if (t <= 4.2e-72) {
tmp = fma(((z - t) / a), y, x);
} else {
tmp = t_1;
}
return tmp;
}
function code(x, y, z, t, a) t_1 = fma(Float64(1.0 - Float64(z / t)), y, x) tmp = 0.0 if (t <= -6e-47) tmp = t_1; elseif (t <= 4.2e-72) tmp = fma(Float64(Float64(z - t) / a), y, x); else tmp = t_1; end return tmp end
code[x_, y_, z_, t_, a_] := Block[{t$95$1 = N[(N[(1.0 - N[(z / t), $MachinePrecision]), $MachinePrecision] * y + x), $MachinePrecision]}, If[LessEqual[t, -6e-47], t$95$1, If[LessEqual[t, 4.2e-72], N[(N[(N[(z - t), $MachinePrecision] / a), $MachinePrecision] * y + x), $MachinePrecision], t$95$1]]]
\begin{array}{l}
\\
\begin{array}{l}
t_1 := \mathsf{fma}\left(1 - \frac{z}{t}, y, x\right)\\
\mathbf{if}\;t \leq -6 \cdot 10^{-47}:\\
\;\;\;\;t\_1\\
\mathbf{elif}\;t \leq 4.2 \cdot 10^{-72}:\\
\;\;\;\;\mathsf{fma}\left(\frac{z - t}{a}, y, x\right)\\
\mathbf{else}:\\
\;\;\;\;t\_1\\
\end{array}
\end{array}
if t < -6.00000000000000033e-47 or 4.2e-72 < t Initial program 79.6%
Taylor expanded in a around 0
+-commutativeN/A
mul-1-negN/A
associate-/l*N/A
*-commutativeN/A
distribute-lft-neg-inN/A
lower-fma.f64N/A
neg-sub0N/A
div-subN/A
*-inversesN/A
associate-+l-N/A
neg-sub0N/A
mul-1-negN/A
+-commutativeN/A
mul-1-negN/A
unsub-negN/A
lower--.f64N/A
lower-/.f6491.2
Applied rewrites91.2%
if -6.00000000000000033e-47 < t < 4.2e-72Initial program 92.7%
Taylor expanded in a around inf
+-commutativeN/A
associate-/l*N/A
*-commutativeN/A
lower-fma.f64N/A
lower-/.f64N/A
lower--.f6489.4
Applied rewrites89.4%
(FPCore (x y z t a) :precision binary64 (let* ((t_1 (fma (- 1.0 (/ z t)) y x))) (if (<= t -6e-47) t_1 (if (<= t 8.2e-72) (fma (/ z a) y x) t_1))))
double code(double x, double y, double z, double t, double a) {
double t_1 = fma((1.0 - (z / t)), y, x);
double tmp;
if (t <= -6e-47) {
tmp = t_1;
} else if (t <= 8.2e-72) {
tmp = fma((z / a), y, x);
} else {
tmp = t_1;
}
return tmp;
}
function code(x, y, z, t, a) t_1 = fma(Float64(1.0 - Float64(z / t)), y, x) tmp = 0.0 if (t <= -6e-47) tmp = t_1; elseif (t <= 8.2e-72) tmp = fma(Float64(z / a), y, x); else tmp = t_1; end return tmp end
code[x_, y_, z_, t_, a_] := Block[{t$95$1 = N[(N[(1.0 - N[(z / t), $MachinePrecision]), $MachinePrecision] * y + x), $MachinePrecision]}, If[LessEqual[t, -6e-47], t$95$1, If[LessEqual[t, 8.2e-72], N[(N[(z / a), $MachinePrecision] * y + x), $MachinePrecision], t$95$1]]]
\begin{array}{l}
\\
\begin{array}{l}
t_1 := \mathsf{fma}\left(1 - \frac{z}{t}, y, x\right)\\
\mathbf{if}\;t \leq -6 \cdot 10^{-47}:\\
\;\;\;\;t\_1\\
\mathbf{elif}\;t \leq 8.2 \cdot 10^{-72}:\\
\;\;\;\;\mathsf{fma}\left(\frac{z}{a}, y, x\right)\\
\mathbf{else}:\\
\;\;\;\;t\_1\\
\end{array}
\end{array}
if t < -6.00000000000000033e-47 or 8.20000000000000007e-72 < t Initial program 79.6%
Taylor expanded in a around 0
+-commutativeN/A
mul-1-negN/A
associate-/l*N/A
*-commutativeN/A
distribute-lft-neg-inN/A
lower-fma.f64N/A
neg-sub0N/A
div-subN/A
*-inversesN/A
associate-+l-N/A
neg-sub0N/A
mul-1-negN/A
+-commutativeN/A
mul-1-negN/A
unsub-negN/A
lower--.f64N/A
lower-/.f6491.2
Applied rewrites91.2%
if -6.00000000000000033e-47 < t < 8.20000000000000007e-72Initial program 92.7%
Taylor expanded in t around 0
+-commutativeN/A
associate-/l*N/A
*-commutativeN/A
lower-fma.f64N/A
lower-/.f6483.6
Applied rewrites83.6%
(FPCore (x y z t a) :precision binary64 (if (<= t -1.02e+93) (+ x y) (if (<= t 4.7e+44) (fma (/ z a) y x) (+ x y))))
double code(double x, double y, double z, double t, double a) {
double tmp;
if (t <= -1.02e+93) {
tmp = x + y;
} else if (t <= 4.7e+44) {
tmp = fma((z / a), y, x);
} else {
tmp = x + y;
}
return tmp;
}
function code(x, y, z, t, a) tmp = 0.0 if (t <= -1.02e+93) tmp = Float64(x + y); elseif (t <= 4.7e+44) tmp = fma(Float64(z / a), y, x); else tmp = Float64(x + y); end return tmp end
code[x_, y_, z_, t_, a_] := If[LessEqual[t, -1.02e+93], N[(x + y), $MachinePrecision], If[LessEqual[t, 4.7e+44], N[(N[(z / a), $MachinePrecision] * y + x), $MachinePrecision], N[(x + y), $MachinePrecision]]]
\begin{array}{l}
\\
\begin{array}{l}
\mathbf{if}\;t \leq -1.02 \cdot 10^{+93}:\\
\;\;\;\;x + y\\
\mathbf{elif}\;t \leq 4.7 \cdot 10^{+44}:\\
\;\;\;\;\mathsf{fma}\left(\frac{z}{a}, y, x\right)\\
\mathbf{else}:\\
\;\;\;\;x + y\\
\end{array}
\end{array}
if t < -1.0200000000000001e93 or 4.70000000000000018e44 < t Initial program 71.0%
Taylor expanded in t around inf
+-commutativeN/A
lower-+.f6486.9
Applied rewrites86.9%
if -1.0200000000000001e93 < t < 4.70000000000000018e44Initial program 95.2%
Taylor expanded in t around 0
+-commutativeN/A
associate-/l*N/A
*-commutativeN/A
lower-fma.f64N/A
lower-/.f6472.7
Applied rewrites72.7%
Final simplification79.1%
(FPCore (x y z t a) :precision binary64 (if (<= t -3.5e-106) (+ x y) (if (<= t 2.5e-122) (* (/ z a) y) (+ x y))))
double code(double x, double y, double z, double t, double a) {
double tmp;
if (t <= -3.5e-106) {
tmp = x + y;
} else if (t <= 2.5e-122) {
tmp = (z / a) * y;
} else {
tmp = x + y;
}
return tmp;
}
real(8) function code(x, y, z, t, a)
real(8), intent (in) :: x
real(8), intent (in) :: y
real(8), intent (in) :: z
real(8), intent (in) :: t
real(8), intent (in) :: a
real(8) :: tmp
if (t <= (-3.5d-106)) then
tmp = x + y
else if (t <= 2.5d-122) then
tmp = (z / a) * y
else
tmp = x + y
end if
code = tmp
end function
public static double code(double x, double y, double z, double t, double a) {
double tmp;
if (t <= -3.5e-106) {
tmp = x + y;
} else if (t <= 2.5e-122) {
tmp = (z / a) * y;
} else {
tmp = x + y;
}
return tmp;
}
def code(x, y, z, t, a): tmp = 0 if t <= -3.5e-106: tmp = x + y elif t <= 2.5e-122: tmp = (z / a) * y else: tmp = x + y return tmp
function code(x, y, z, t, a) tmp = 0.0 if (t <= -3.5e-106) tmp = Float64(x + y); elseif (t <= 2.5e-122) tmp = Float64(Float64(z / a) * y); else tmp = Float64(x + y); end return tmp end
function tmp_2 = code(x, y, z, t, a) tmp = 0.0; if (t <= -3.5e-106) tmp = x + y; elseif (t <= 2.5e-122) tmp = (z / a) * y; else tmp = x + y; end tmp_2 = tmp; end
code[x_, y_, z_, t_, a_] := If[LessEqual[t, -3.5e-106], N[(x + y), $MachinePrecision], If[LessEqual[t, 2.5e-122], N[(N[(z / a), $MachinePrecision] * y), $MachinePrecision], N[(x + y), $MachinePrecision]]]
\begin{array}{l}
\\
\begin{array}{l}
\mathbf{if}\;t \leq -3.5 \cdot 10^{-106}:\\
\;\;\;\;x + y\\
\mathbf{elif}\;t \leq 2.5 \cdot 10^{-122}:\\
\;\;\;\;\frac{z}{a} \cdot y\\
\mathbf{else}:\\
\;\;\;\;x + y\\
\end{array}
\end{array}
if t < -3.5e-106 or 2.4999999999999999e-122 < t Initial program 81.6%
Taylor expanded in t around inf
+-commutativeN/A
lower-+.f6473.2
Applied rewrites73.2%
if -3.5e-106 < t < 2.4999999999999999e-122Initial program 91.7%
Taylor expanded in z around inf
associate-/l*N/A
*-commutativeN/A
lower-*.f64N/A
lower-/.f64N/A
lower--.f6455.1
Applied rewrites55.1%
Taylor expanded in a around inf
Applied rewrites49.5%
Final simplification66.8%
(FPCore (x y z t a) :precision binary64 (if (<= y 5.3e+168) (+ x y) (/ (* y z) a)))
double code(double x, double y, double z, double t, double a) {
double tmp;
if (y <= 5.3e+168) {
tmp = x + y;
} else {
tmp = (y * z) / a;
}
return tmp;
}
real(8) function code(x, y, z, t, a)
real(8), intent (in) :: x
real(8), intent (in) :: y
real(8), intent (in) :: z
real(8), intent (in) :: t
real(8), intent (in) :: a
real(8) :: tmp
if (y <= 5.3d+168) then
tmp = x + y
else
tmp = (y * z) / a
end if
code = tmp
end function
public static double code(double x, double y, double z, double t, double a) {
double tmp;
if (y <= 5.3e+168) {
tmp = x + y;
} else {
tmp = (y * z) / a;
}
return tmp;
}
def code(x, y, z, t, a): tmp = 0 if y <= 5.3e+168: tmp = x + y else: tmp = (y * z) / a return tmp
function code(x, y, z, t, a) tmp = 0.0 if (y <= 5.3e+168) tmp = Float64(x + y); else tmp = Float64(Float64(y * z) / a); end return tmp end
function tmp_2 = code(x, y, z, t, a) tmp = 0.0; if (y <= 5.3e+168) tmp = x + y; else tmp = (y * z) / a; end tmp_2 = tmp; end
code[x_, y_, z_, t_, a_] := If[LessEqual[y, 5.3e+168], N[(x + y), $MachinePrecision], N[(N[(y * z), $MachinePrecision] / a), $MachinePrecision]]
\begin{array}{l}
\\
\begin{array}{l}
\mathbf{if}\;y \leq 5.3 \cdot 10^{+168}:\\
\;\;\;\;x + y\\
\mathbf{else}:\\
\;\;\;\;\frac{y \cdot z}{a}\\
\end{array}
\end{array}
if y < 5.29999999999999973e168Initial program 84.8%
Taylor expanded in t around inf
+-commutativeN/A
lower-+.f6466.6
Applied rewrites66.6%
if 5.29999999999999973e168 < y Initial program 80.4%
Taylor expanded in z around inf
associate-/l*N/A
*-commutativeN/A
lower-*.f64N/A
lower-/.f64N/A
lower--.f6459.8
Applied rewrites59.8%
Taylor expanded in a around inf
Applied rewrites46.5%
Final simplification64.3%
(FPCore (x y z t a) :precision binary64 (+ x y))
double code(double x, double y, double z, double t, double a) {
return x + y;
}
real(8) function code(x, y, z, t, a)
real(8), intent (in) :: x
real(8), intent (in) :: y
real(8), intent (in) :: z
real(8), intent (in) :: t
real(8), intent (in) :: a
code = x + y
end function
public static double code(double x, double y, double z, double t, double a) {
return x + y;
}
def code(x, y, z, t, a): return x + y
function code(x, y, z, t, a) return Float64(x + y) end
function tmp = code(x, y, z, t, a) tmp = x + y; end
code[x_, y_, z_, t_, a_] := N[(x + y), $MachinePrecision]
\begin{array}{l}
\\
x + y
\end{array}
Initial program 84.3%
Taylor expanded in t around inf
+-commutativeN/A
lower-+.f6461.6
Applied rewrites61.6%
Final simplification61.6%
(FPCore (x y z t a) :precision binary64 (+ x (/ y (/ (- a t) (- z t)))))
double code(double x, double y, double z, double t, double a) {
return x + (y / ((a - t) / (z - t)));
}
real(8) function code(x, y, z, t, a)
real(8), intent (in) :: x
real(8), intent (in) :: y
real(8), intent (in) :: z
real(8), intent (in) :: t
real(8), intent (in) :: a
code = x + (y / ((a - t) / (z - t)))
end function
public static double code(double x, double y, double z, double t, double a) {
return x + (y / ((a - t) / (z - t)));
}
def code(x, y, z, t, a): return x + (y / ((a - t) / (z - t)))
function code(x, y, z, t, a) return Float64(x + Float64(y / Float64(Float64(a - t) / Float64(z - t)))) end
function tmp = code(x, y, z, t, a) tmp = x + (y / ((a - t) / (z - t))); end
code[x_, y_, z_, t_, a_] := N[(x + N[(y / N[(N[(a - t), $MachinePrecision] / N[(z - t), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]
\begin{array}{l}
\\
x + \frac{y}{\frac{a - t}{z - t}}
\end{array}
herbie shell --seed 2024249
(FPCore (x y z t a)
:name "Graphics.Rendering.Plot.Render.Plot.Axis:renderAxisTicks from plot-0.2.3.4, B"
:precision binary64
:alt
(! :herbie-platform default (+ x (/ y (/ (- a t) (- z t)))))
(+ x (/ (* y (- z t)) (- a t))))