Clamping the dot product in a Slerp for Quaternion

I'm looking at two different source for the Slerp method of interpolation between two quaternions. They are pretty similar except for one notable difference: one clamps the dot product between 0 and 1, and the other between -1 and 1. Here is one of them:

Code :

glm::fquat Slerp(const glm::fquat &v0, const glm::fquat &v1, float alpha)
{
float dot = glm::dot(v0, v1);
const float DOT_THRESHOLD = 0.9995f;
if (dot > DOT_THRESHOLD)
return Lerp(v0, v1, alpha);
glm::clamp(dot, -1.0f, 1.0f); //<-- The line in question
float theta_0 = acosf(dot);
float theta = theta_0*alpha;
glm::fquat v2 = v1 - v0*dot;
v2 = glm::normalize(v2);
return v0*cos(theta) + v2*sin(theta);
}

Here is the other:

Code :

template <typename T>
inline QuaternionT<T> QuaternionT<T>::Slerp(T t, const QuaternionT<T>& v1) const
{
const T epsilon = 0.0005f;
T dot = Dot(v1);
if (dot > 1 - epsilon) {
QuaternionT<T> result = v1 + (*this - v1).Scaled(t);
result.Normalize();
return result;
}
if (dot < 0) //<-The lower clamp
dot = 0;
if (dot > 1)
dot = 1;
T theta0 = std::acos(dot);
T theta = theta0 * t;
QuaternionT<T> v2 = (v1 - Scaled(dot));
v2.Normalize();
QuaternionT<T> q = Scaled(std::cos(theta)) + v2.Scaled(std::sin(theta));
q.Normalize();
return q;
}

I think it is worth noting also the the Lerp algorithm in the second one doesn't seem right for all cases?

I just want some feedback on these differences and if they really matter at all.