BALANCED\_MOD _ _ _ _ _ _ _ _ _ _ _ _ switch
modularnumbers are normally produced in the range [0,. ..<n>), where <n> is the current modulus. With balanced_mod on, the range [-<n>/2,<n>/2], or more precisely [-floor((<n>-1)/2), ceiling((<n>-1)/2)], is used instead.
setmod 7; 1 on modular; 4; 4 on balanced_mod; 4; -3