In the lazy evaluation page it says:

bool scase(bool b, lazy void dg)
{
    if (b)
    {	dg();
	return true;
    }
    return false;
}


That is somehow unnecessary doubled precision. The following code should do the same:

bool scase(bool b, lazy void dg)
{
    if (b) dg();
    return b;
}

You're right.