⇔ (left right double arrow)
The logical equivalence operator.
Syntax

p ⇔ q

p
andq
are booleans

Description
⇔
is the logical equivalence operator. The truth table for ⇔
is as follows:
qp

false  true 

false  true  false 
true  false  true 
⇔
is a binary operator implemented by the equivalent
function.
Notes
For booleans, the value of p ⇔ q
is equal to the value of p = q
, but the latter expression is also defined for nonboolean objects.
See also

Logical operators (list)