public Builder<T> lparen(final Predicate<? super T> lparen) {
			_lparen = requireNonNull(lparen);
			return this;
		}
Set the predicate which defines {@code lparen} tokens. If the given
predicate returns {@code true} for a token, it is treated as
<em>lparen</em>.

@param lparen the {@code lparen} token
@return {@code this} builder, for method chaining
@throws NullPointerException if the {@code lparen} is {@code null}
jenetics.ext/src/main/java/io/jenetics/ext/internal/util/FormulaParser.java