Andrey Semashev wrote:
I don't think that the ternary operator and a throw expression is a constant expression that can be used in a constexpr function. In 5.19/2, the throw expression is explicitly mentioned as the one that cannot make a constant expression.
I suspect that you've missed the "but subexpressions of logical AND (5.14), logical OR (5.15), and conditional (5.16) operations that are not evaluated are not considered" part. You can have a throw expression, as long as it's not evaluated.
In fact, I cannot see how a constant expression (such as a constexpr function) can throw.
A constexpr function can throw when it's called with an argument that is not a constant expression. On second thought, this perhaps does make it possible to have something assert-like in a constexpr function. constexpr const_reference operator[]( size_type i ) const { return i < size()? elems[i]: ( abort(), elems[i] ); // or // return i < size()? elems[i]: ( abort(), throw 0 ); }