∉ (not an element of)
Tests for set nonmembership.
Syntax

a ∉ A

a
is any object 
A
is a set

Description
If a
is any object and A
a set, then a ∉ A
returns true
iff a
is not an element of A
.
If the cardinality of A
is reasonably small, floatingpoint values are compared individually with epsilon. However, if the cardinality is very large, a different algorithm may be used to improve performance, which may not be epsilonbased.
The ∉
operator is implemented by the NotElementOf
function.
Examples
A ≔ {−1, 0, 1}
{1, −1, 0}
sin(π) ∉ A
false
See also

Set operators (list)