Returns the hyperbolic arc-tangent of x.
Special Cases:
pub fn atanh(x: anytype) @TypeOf(x)
pub fn atanh(x: anytype) @TypeOf(x) { const T = @TypeOf(x); return switch (T) { f32 => atanh_32(x), f64 => atanh_64(x), else => @compileError("atanh not implemented for " ++ @typeName(T)), }; }