@SafeVarargs
			public final Builder<T> E(final Symbol<T>... symbols) {
				expressions.add(Cfg.E(symbols));
				return this;
			}
Builder method for creating an expression with the given
{@code symbols}.

@param symbols the expression symbols
@throws IllegalArgumentException if the list of {@code symbols}
        is empty
@return {@code this} builder for method chaining
jenetics.ext/src/main/java/io/jenetics/ext/grammar/Cfg.java