Fold Expressions are supported for the following operators
| + | - | * | / | % | \ˆ | & | | | << | >> | ||
| += | -= | *= | /= | %= | \ˆ= | &= | |= | <<= | >>= | = | |
| == | != | < | > | <= | >= | && | || | , | .* | ->* | 
When folding over an empty sequence, a fold expression is ill-formed, except for the following three operators:
| Operator | Value when parameter pack is empty | 
|---|---|
| && | true | 
| || | false | 
| , | void() | 
 
                