code: public static <R> IntFunction<R> intFunction(CheckedIntFunction<R> function) {
          return intFunction(function, THROWABLE_TO_RUNTIME_EXCEPTION);
      }
docs: Wrap a {@link CheckedIntFunction} in a {@link IntFunction}.
  <p>
  Example:
  <code><pre>
  IntStream.of(1, 2, 3).mapToObj(Unchecked.intFunction(i -> {
  if (i &lt; 0)
  throw new Exception("Only positive numbers allowed");
  
  return "" + i;
  });
  </pre></code>