double z = a.getAndUpdate(value -> value + y);
        assertBitEquals(x, z);
        assertBitEquals(x + y, a.get());
      }
    }
  }

  /**
   * getAndUpdate with subtract stores subtraction of value from current, and returns previous value
   */
  public void testGetAndUpdateWithSubtract() {
    for (double x : VALUES) {
      for (double y : VALUES) {
        AtomicDouble a = new AtomicDouble(x);

      sort(
          insertionOrder,
          new Comparator<V>() {
            @Override
            public int compare(V left, V right) {
              // The indexes are small enough for the subtraction trick to be safe.
              return indexOfEntryWithValue(left) - indexOfEntryWithValue(right);
            }

            int indexOfEntryWithValue(V value) {

        };
      }
    };
  }

  /**
   * Returns an unmodifiable view of the difference of two multisets. In the returned multiset, the
   * count of each element is the result of the <i>zero-truncated subtraction</i> of its count in
   * the second multiset from its count in the first multiset, with elements that would have a count
   * of 0 not included. The iteration order of the returned multiset matches that of the element set

        };
      }
    };
  }

  /**
   * Returns an unmodifiable view of the difference of two multisets. In the returned multiset, the
   * count of each element is the result of the <i>zero-truncated subtraction</i> of its count in
   * the second multiset from its count in the first multiset, with elements that would have a count
   * of 0 not included. The iteration order of the returned multiset matches that of the element set

		p.errorf("TEXT %q: ABIInternal requires NOSPLIT", name)
	}

	// Next operand is the frame and arg size.
	// Bizarre syntax: $frameSize-argSize is two words, not subtraction.
	// Both frameSize and argSize must be simple integers; only frameSize
	// can be negative.
	// The "-argSize" may be missing; if so, set it to objabi.ArgsSizeUnknown.
	// Parse left to right.
	op := operands[next]

	MOVQ	CX, 0(SP)
	CALL	runtime·externalthreadhandler(SB)
	RET
</pre>

<p>
In the general case, the frame size is followed by an argument size, separated by a minus sign.
(It's not a subtraction, just idiosyncratic syntax.)
The frame size <code>$24-8</code> states that the function has a 24-byte frame
and is called with 8 bytes of argument, which live on the caller's frame.

0.15e+0_2    // == 15.0

0x1p-2       // == 0.25
0x2.p10      // == 2048.0
0x1.Fp+0     // == 1.9375
0X.8p-0      // == 0.5
0X_1FFFP-16  // == 0.1249847412109375
0x15e-2      // == 0x15e - 2 (integer subtraction)

0x.p1        // invalid: mantissa has no digits
1p-2         // invalid: p exponent requires hexadecimal mantissa
0x1.5e-2     // invalid: hexadecimal mantissa requires p exponent

   *
   * @since 14.0
   */
  public UnsignedInteger plus(UnsignedInteger val) {
    return fromIntBits(this.value + checkNotNull(val).value);
  }

  /**
   * Returns the result of subtracting this and {@code val}. If the result would be negative,
   * returns the low 32 bits of the result.
   *
   * @since 14.0
   */
  public UnsignedInteger minus(UnsignedInteger val) {

   *
   * @since 14.0
   */
  public UnsignedInteger plus(UnsignedInteger val) {
    return fromIntBits(this.value + checkNotNull(val).value);
  }

  /**
   * Returns the result of subtracting this and {@code val}. If the result would be negative,
   * returns the low 32 bits of the result.
   *
   * @since 14.0
   */
  public UnsignedInteger minus(UnsignedInteger val) {

0.15e+0_2    // == 15.0

0x1p-2       // == 0.25
0x2.p10      // == 2048.0
0x1.Fp+0     // == 1.9375
0X.8p-0      // == 0.5
0X_1FFFP-16  // == 0.1249847412109375
0x15e-2      // == 0x15e - 2 (integer subtraction)

0x.p1        // invalid: mantissa has no digits
1p-2         // invalid: p exponent requires hexadecimal mantissa
0x1.5e-2     // invalid: hexadecimal mantissa requires p exponent