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Available inall subroutines.

Computes the inverse hyperbolic tangent of its argument x.

Parameters

x - Floating point value representing a hyperbolic angle.

Return Value

Upon successful completion, this function returns the inverse hyperbolic tangent of x.

If x is math.NAN, a NaN will be returned.

If x is ±0, x will be returned.

If x is math.POS_INFINITY or math.NEG_INFINITY, a domain error occurs and a NaN will be returned.

If x is subnormal, a range error occurs and x will be returned.

For finite |x|>1, a domain error occurs and a NaN will be returned.

If x is ±1, a pole error occurs, and math.atanh will return the value of the macro math.POS_HUGE_VAL or math.NEG_HUGE_VAL with the same sign as the result of the function.

Errors

• If the x argument is finite and not in the range -1 to 1 inclusive, or if it is math.POS_INFINITY or math.NEG_INFINITY, then fastly.error will be set to EDOM.
• If the x argument is subnormal, or ±1, then fastly.error will be set to ERANGE.

Example

declare local var.fo FLOAT;

set var.fo = math.atanh(-1); // Returns `math.NEG_INFINITY`

if (fastly.error) {
  set resp.http.atanh-error = fastly.error; // Returns "ERANGE"
}