FICS formula and logic

FICS formula supports Boolean algebra.
[ a ⇒ b ] ⇔ [ (¬a) ∨ b ] ⇔ [ (¬a) ∨ (b ∧ a) ]
In this case the rightmost expression lets us better understand the leftmost.
Example: FICS formula !chess | etime>=15 is equivalent to !chess | (chess & etime>=15). From the right(colored in green) formula is clear what the left(and right) formula will do - It will make you accessible to all !chess boards' seek advertisements(ads), plus, chess board ads those etime is equal or more then 15.

Links:
Table_of_logic_symbols, Logical_connective, Propositional_logic, Boolean_algebra_(structure), Two-element_Boolean_algebra.