Add vec explicit conversion

adoc/chapters/programming_interface.adoc

@@ -17869,6 +17869,21 @@ to which [code]#DataT# is implicitly convertible.
 Note that conversion operator shall not be templated
 to allow standard conversion sequence for implicit conversion.
 
+a@
+[source]
+----
+template<typename T>
+explicit operator T() const
+----
+a@ _Constraints:_
+
+* [code]#NumElements# is equal to 1, and
+* [code]#DataT# can be explicitly converted to [code]#T# via
+  [code]#static_cast<T>#, and
+* [code]#T# is not [code]#DataT#.
+
+Returns the value of the vector's element converted to [code]#T#.
+
 a@
 [source]
 ----
@@ -18661,6 +18676,10 @@ operator vector_t() const
 #endif
 
 operator DataT() const
+
+template<typename T>
+explicit operator T() const
+
 static constexpr size_t byte_size() noexcept
 static constexpr size_t size() noexcept
 

adoc/headers/vec.h

@@ -58,6 +58,10 @@ template <typename DataT, int NumElements> class vec {
   // Available only when: NumElements == 1
   operator DataT() const;
 
+  // Available only when: NumElements == 1 and T is explicitly convertible to DataT
+  template<typename T>
+  explicit operator T() const;
+
   static constexpr size_t byte_size() noexcept;
 
   static constexpr size_t size() noexcept;