Code review request for 6560935: BigInteger.modPow() throws ArithmeticException for negative exponent (original) (raw)

Joseph D. Darcy Joe.Darcy at Sun.COM
Tue Oct 20 21:45:13 UTC 2009

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Hello.

Please review this small doc clarification; modPow is not defined for negative exponents unless the BigInteger being operated on is relatively prime to the modulus. There are a few stylistic javadoc cleanups in the patch below too.

Webrev: http://cr.openjdk.java.net/~darcy/6560935.0/

Thanks,

-Joe

--- old/src/share/classes/java/math/BigInteger.java 2009-10-20 14:40:35.000000000 -0700 +++ new/src/share/classes/java/math/BigInteger.java 2009-10-20 14:40:35.000000000 -0700 @@ -478,7 +478,7 @@

 /**
  * Constructs a randomly generated BigInteger, uniformly 

distributed over

• * the range {@code 0} to (2<sup>{@code numBits}</sup> - 1), inclusive.

• * the range 0 to (2<sup>{@code numBits}</sup> - 1), inclusive.
  * The uniformity of the distribution assumes that a fair source of

random * bits is provided in {@code rnd}. Note that this constructor always * constructs a non-negative BigInteger. @@ -1332,7 +1332,7 @@ * * @param val value by which this BigInteger is to be divided. * @return {@code this / val}

• * @throws ArithmeticException {@code val==0}

• * @throws ArithmeticException if {@code val} is zero.
  */

  public BigInteger divide(BigInteger val) { MutableBigInteger q = new MutableBigInteger(),

@@ -1352,7 +1352,7 @@ * @return an array of two BigIntegers: the quotient {@code (this / val)} * is the initial element, and the remainder {@code (this % val)} * is the final element.

• * @throws ArithmeticException {@code val==0}

• * @throws ArithmeticException if {@code val} is zero.
  */

  public BigInteger[] divideAndRemainder(BigInteger val) { BigInteger[] result = new BigInteger[2];

@@ -1371,7 +1371,7 @@ * @param val value by which this BigInteger is to be divided, and the * remainder computed. * @return {@code this % val}

• * @throws ArithmeticException {@code val==0}

• * @throws ArithmeticException if {@code val} is zero.
  */

  public BigInteger remainder(BigInteger val) { MutableBigInteger q = new MutableBigInteger(),

@@ -1547,7 +1547,7 @@ * * @param m the modulus. * @return {@code this mod m}

• * @throws ArithmeticException {@code m <= 0}

• * @throws ArithmeticException {@code m} ≤ 0
  * @see    #remainder
  */

  public BigInteger mod(BigInteger m) { @@ -1566,7 +1566,9 @@ * @param exponent the exponent. * @param m the modulus. * @return this^exponent mod m

• * @throws ArithmeticException {@code m <= 0}

• * @throws ArithmeticException {@code m} ≤ 0 or the exponent is

• *         negative and this BigInteger is not <i>relatively

• *         prime</i> to m.
  * @see    #modInverse
  */

  public BigInteger modPow(BigInteger exponent, BigInteger m) { @@ -2015,7 +2017,7 @@ * * @param m the modulus. * @return {@code this}^-1 {@code mod m}.

• * @throws ArithmeticException {@code  m <= 0}, or this BigInteger

• * @throws ArithmeticException {@code  m} ≤ 0, or this BigInteger
  *         has no multiplicative inverse mod m (that is, this

BigInteger * is not relatively prime to m). / @@ -2449,7 +2451,7 @@ /* * Returns {@code true} if this BigInteger is probably prime, * {@code false} if it's definitely composite. If

• * {@code certainty} is {@code  <= 0}, {@code true} is

• * {@code certainty} is ≤ 0, {@code true} is
  * returned.
  *
  * @param  certainty a measure of the uncertainty that the caller is

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