Ternary conditionals
The syntax condition ?? thenExpr !! elseExpr
is introduced
as an alternative for if (condition) then thenExpr else elseExpr
.
The semantics are identical.
The operator syntax is borrowed from Raku (formerly Perl6), other operators such as "?" and ":" being unavailable for the purpose.
This feature has recently been dropped from the draft specification, so it should not be used. It will be removed in a future Saxon release.