Synopsis Test whether the value of an expression is defined.
Syntax
Exp ?
Types
Exp | Exp ? |
|---|---|
T | bool |
Description If no exception is generated during the evaluation of
Exp,
the result is true. Otherwise, it is false.
Examples
rascal>T = ("a" : 1, "b" : 2); map[str, int]: ("a":1,"b":2) rascal>T["b"]? bool: true rascal>T["c"]? bool: false rascal>L = [10, 20, 30]; list[int]: [10,20,30] rascal>L[1]? bool: true rascal>L[5]? bool: false