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(datatype Math
(Num i64)
(Var String)
(Mul Math Math))
(function hi (Math) i64 :merge (min old new))
(function lo (Math) i64 :merge (max old new))
(rule ((= mul (Mul a b))
(= loa (lo a))
(= lob (lo b))
(= hia (hi a))
(= hib (hi b))
)
((set (lo mul)
(min (min (* loa lob) (* loa hib))
(min (* hia lob) (* hia hib))))))
(let $x (Var "x"))
(let $e (Mul $x $x))
(set (lo $x) -10)
(set (hi $x) 10)
(run 1)
(check (= (lo $e) -100))
(rule ((= mul (Mul a a))
(= loa (lo a))
)
((set (lo mul) (* loa loa))))
(run 1)
(check (= (lo $e) 100))
;; testing extraction of rationals
(extract (lo $e))