public Builder<T> rparen(final T rparen) {
			return rparen(token -> Objects.equals(token, rparen));
		}
Set the <em>prototype</em> for the {@code rparen} token. A given
token is treated as  {@code rparen} if {@code Objects.equals(token, rparen)}
returns {@code true}.

@param rparen the {@code rparen} prototype
@return {@code this} builder, for method chaining
jenetics.ext/src/main/java/io/jenetics/ext/internal/util/FormulaParser.java