In a Restriction, no pair of parentheses (or other symbols of grouping) may enclose an = or C symbol. However, a player may put parentheses around the entire Restriction, like this: (B C R U G). Or around one side of a Restriction, like this: B C (R U G). While useless, these parentheses do not make the Restriction wrong.
A common error is putting parentheses around part of a chain Restriction, like this where A, B, and C are sets: (A C B) C C, A = (B = C), and so on. Such parentheses make the chain meaningless just as the parentheses in the algebraic equation (2x=3)+7 make it meaningless. Also these parentheses are inappropriate: (B = R)’
However, this does not mean that parentheses may not be used at all in Restrictions. Parentheses may legitimately be placed within any Set-Name in a Restriction, as in the following examples. (Notice in these examples that no pair of parentheses encloses an = or C.)
(R U B) â€“ G = V, B = (G U R)’ C V, R’ = B C (R â€“ Y) U V