section‹Operations› theory Operations imports Main begin class left_imp = fixes imp_l :: "'a ⇒ 'a ⇒ 'a" (infixr "l→" 65) class right_imp = fixes imp_r :: "'a ⇒ 'a ⇒ 'a" (infixr "r→" 65) class left_uminus = fixes uminus_l :: "'a => 'a" ("-l _" [81] 80) class right_uminus = fixes uminus_r :: "'a => 'a" ("-r _" [81] 80) end