\sqrt{\frac{e^{2 \cdot x} - 1}{e^{x} - 1}}\begin{array}{l}
\mathbf{if}\;x \le -1.635655884635412785585475300345031302932 \cdot 10^{-16}:\\
\;\;\;\;\sqrt{\frac{e^{2 \cdot x} - 1}{e^{x + x} - 1 \cdot 1}} \cdot \sqrt{e^{x} + 1}\\
\mathbf{else}:\\
\;\;\;\;\left(\sqrt{2} + 0.5 \cdot \frac{x}{\sqrt{2}}\right) + \frac{{x}^{2}}{\sqrt{2}} \cdot \left(0.25 - \frac{0.125}{2}\right)\\
\end{array}double f(double x) {
double r24085 = 2.0;
double r24086 = x;
double r24087 = r24085 * r24086;
double r24088 = exp(r24087);
double r24089 = 1.0;
double r24090 = r24088 - r24089;
double r24091 = exp(r24086);
double r24092 = r24091 - r24089;
double r24093 = r24090 / r24092;
double r24094 = sqrt(r24093);
return r24094;
}
double f(double x) {
double r24095 = x;
double r24096 = -1.6356558846354128e-16;
bool r24097 = r24095 <= r24096;
double r24098 = 2.0;
double r24099 = r24098 * r24095;
double r24100 = exp(r24099);
double r24101 = 1.0;
double r24102 = r24100 - r24101;
double r24103 = r24095 + r24095;
double r24104 = exp(r24103);
double r24105 = r24101 * r24101;
double r24106 = r24104 - r24105;
double r24107 = r24102 / r24106;
double r24108 = sqrt(r24107);
double r24109 = exp(r24095);
double r24110 = r24109 + r24101;
double r24111 = sqrt(r24110);
double r24112 = r24108 * r24111;
double r24113 = sqrt(r24098);
double r24114 = 0.5;
double r24115 = r24095 / r24113;
double r24116 = r24114 * r24115;
double r24117 = r24113 + r24116;
double r24118 = 2.0;
double r24119 = pow(r24095, r24118);
double r24120 = r24119 / r24113;
double r24121 = 0.25;
double r24122 = 0.125;
double r24123 = r24122 / r24098;
double r24124 = r24121 - r24123;
double r24125 = r24120 * r24124;
double r24126 = r24117 + r24125;
double r24127 = r24097 ? r24112 : r24126;
return r24127;
}



Bits error versus x
Results
if x < -1.6356558846354128e-16Initial program 0.8
rmApplied flip--0.6
Applied associate-/r/0.6
Applied sqrt-prod0.6
Simplified0.0
if -1.6356558846354128e-16 < x Initial program 38.4
Taylor expanded around 0 9.1
Simplified9.1
Final simplification0.9
herbie shell --seed 2019305
(FPCore (x)
:name "sqrtexp (problem 3.4.4)"
:precision binary64
(sqrt (/ (- (exp (* 2 x)) 1) (- (exp x) 1))))