std::extents<IndexType,Extents...>::fwd-prod-of-extents
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                    |   constexpr std::size_t /*fwd-prod-of-extents*/( rank_type i ) const noexcept;  | 
 (since C++23)  (exposition only*)  | 
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Returns the product of the sizes of extents with index less than i. The behavior is undefined if i <= rank() is false.
Parameters
| i | - | The end index of the range of extents to be multiplied together. | 
Return value
If i > 0 is true, return the product of extent(k) for all k in range [0, i), otherwise 1.
See also
 returns the product of extents size in range [i + 1, rank())(exposition-only member function*)  |