...one of the most highly
regarded and expertly designed C++ library projects in the
world.
— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards
Returns true
if the object
represents an actual server statement.
bool valid() const;
Calling any function other than assignment on a statement for which this
function returns false
results
in undefined behavior.
Returns false
for default-constructed
statements.
No-throw guarantee.