Synopsis Negated Match operator.
Syntax Pat !:= Exp
Pat Exp Pat !:= Exp
Patterns value bool
Description See PatternMatching for an introduction to pattern matching and Patterns for a complete description.
rascal>123 !:= 456;
bool: true
rascal>[10, N*, 50] !:= [10, 20, 30, 40, 50];
bool: false
rascal>{10, set[int] S, 50} !:= {50, 40, 30, 30, 10};
bool: true
Is this page unclear, or have you spotted an error? Please add a comment below and help us to improve it. For all other questions and remarks, visit