Boolean IsDefined

rascal-0.40.17

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