The operator if...then returns the value of query if the boolean query is true, and empty list otherwise.
The operator if...then...else returns the value of query1 if the boolean query is true, and the value of query2 otherwise.
Prototypes
query <-- if boolean then query
query <-- if boolean then query1 else query2
Examples
- if (2 == 2) then 3;
3if (2 == 4) then 3; if (2 == 4) then 3 else 5; 5