19 General utilities library [utilities]

19.6 Optional objects [optional]

19.6.3 Class template optional [optional.optional]

19.6.3.6 Modifiers [optional.mod]

void reset() noexcept;
Effects: If *this contains a value, calls val->T::~T() to destroy the contained value; otherwise no effect.
Ensures: *this does not contain a value.