public static RatNum make(IntNum num, IntNum den)
{
IntNum g = IntNum.gcd (num, den);
if (den.isNegative ())
g = IntNum.neg (g);
if (! g.isOne ())
{
num = IntNum.quotient (num, g);
den = IntNum.quotient (den, g);
}
return den.isOne () ? (RatNum)num : (RatNum)(new IntFraction (num, den));
}
/** Calculate the integral power of an IntNum.
* @param x the value (base) to exponentiate
* @param y the exponent (must be non-negative)
*/
public static IntNum power(IntNum x, int y)
{
if (y <= 0)
{
if (y == 0)
return one ();
else
throw new Exception ("negative exponent");
}
if (x.isZero ())
return x;
int plen = x.words == null ? 1 : x.ival; // Length of pow2.
int blen = ((x.intLength () * y) >> 5) + 2 * plen;
bool negative = x.isNegative () && (y & 1) != 0;
int[] pow2 = new int [blen];
int[] rwords = new int [blen];
int[] work = new int [blen];
x.getAbsolute (pow2); // pow2 = abs(x);
int rlen = 1;
rwords[0] = 1; // rwords = 1;
for (;;) // for (i = 0; ; i++)
{
// pow2 == x**(2**i)
// prod = x**(sum(j=0..i-1, (y>>j)&1))
if ((y & 1) != 0)
{ // r *= pow2
MPN.mul (work, pow2, plen, rwords, rlen);
int[] tempx = work; work = rwords; rwords = tempx;
rlen += plen;
while (rwords[rlen-1] == 0) rlen--;
}
y >>= 1;
if (y == 0)
break;
// pow2 *= pow2;
MPN.mul (work, pow2, plen, pow2, plen);
int[] temp = work; work = pow2; pow2 = temp; // swap to avoid a copy
plen *= 2;
while (pow2[plen-1] == 0) plen--;
}
if (rwords[rlen-1] < 0)
rlen++;
if (negative)
negate (rwords, rwords, rlen);
return IntNum.make (rwords, rlen);
}
public static IntNum times(IntNum x, IntNum y)
{
if (y.words == null)
return times(x, y.ival);
if (x.words == null)
return times(y, x.ival);
bool negative = false;
int[] xwords;
int[] ywords;
int xlen = x.ival;
int ylen = y.ival;
if (x.isNegative ())
{
negative = true;
xwords = new int[xlen];
negate(xwords, x.words, xlen);
}
else
{
negative = false;
xwords = x.words;
}
if (y.isNegative ())
{
negative = !negative;
ywords = new int[ylen];
negate(ywords, y.words, ylen);
}
else
ywords = y.words;
// Swap if x is shorter then y.
if (xlen < ylen)
{
int[] twords = xwords; xwords = ywords; ywords = twords;
int tlen = xlen; xlen = ylen; ylen = tlen;
}
IntNum result = IntNum.alloc (xlen+ylen);
MPN.mul (result.words, xwords, xlen, ywords, ylen);
result.ival = xlen+ylen;
if (negative)
result.setNegative ();
return result.canonicalize ();
}
/** Divide two integers, yielding quotient and remainder.
* @param x the numerator in the division
* @param y the denominator in the division
* @param quotient is set to the quotient of the result (iff quotient!=null)
* @param remainder is set to the remainder of the result
* (iff remainder!=null)
* @param rounding_mode one of FLOOR, CEILING, TRUNCATE, or ROUND.
*/
public static void divide(IntNum x, IntNum y,
IntNum quotient, IntNum remainder,
int rounding_mode)
{
if ((x.words == null || x.ival <= 2)
&& (y.words == null || y.ival <= 2))
{
long x_l = x.longValue ();
long y_l = y.longValue ();
if (x_l != long.MinValue && y_l != long.MinValue)
{
divide (x_l, y_l, quotient, remainder, rounding_mode);
return;
}
}
bool xNegative = x.isNegative ();
bool yNegative = y.isNegative ();
bool qNegative = xNegative ^ yNegative;
int ylen = y.words == null ? 1 : y.ival;
int[] ywords = new int[ylen];
y.getAbsolute (ywords);
while (ylen > 1 && ywords[ylen-1] == 0) ylen--;
int xlen = x.words == null ? 1 : x.ival;
int[] xwords = new int[xlen+2];
x.getAbsolute (xwords);
while (xlen > 1 && xwords[xlen-1] == 0) xlen--;
int qlen, rlen;
int cmpval = MPN.cmp (xwords, xlen, ywords, ylen);
if (cmpval < 0) // abs(x) < abs(y)
{ // quotient = 0; remainder = num.
int[] rwords = xwords; xwords = ywords; ywords = rwords;
rlen = xlen; qlen = 1; xwords[0] = 0;
}
else if (cmpval == 0) // abs(x) == abs(y)
{
xwords[0] = 1; qlen = 1; // quotient = 1
ywords[0] = 0; rlen = 1; // remainder = 0;
}
else if (ylen == 1)
{
qlen = xlen;
rlen = 1;
ywords[0] = MPN.divmod_1 (xwords, xwords, xlen, ywords[0]);
}
else // abs(x) > abs(y)
{
// Normalize the denominator, i.e. make its most significant bit set by
// shifting it normalization_steps bits to the left. Also shift the
// numerator the same number of steps (to keep the quotient the same!).
int nshift = MPN.count_leading_zeros (ywords[ylen-1]);
if (nshift != 0)
{
// Shift up the denominator setting the most significant bit of
// the most significant word.
MPN.lshift (ywords, 0, ywords, ylen, nshift);
// Shift up the numerator, possibly introducing a new most
// significant word.
int x_high = MPN.lshift (xwords, 0, xwords, xlen, nshift);
xwords[xlen++] = x_high;
}
if (xlen == ylen)
xwords[xlen++] = 0;
MPN.divide (xwords, xlen, ywords, ylen);
rlen = ylen;
MPN.rshift0 (ywords, xwords, 0, rlen, nshift);
qlen = xlen + 1 - ylen;
if (quotient != null)
{
for (int i = 0; i < qlen; i++)
xwords[i] = xwords[i+ylen];
}
}
while (rlen > 1 && ywords[rlen-1] == 0)
rlen--;
if (ywords[rlen-1] < 0)
{
ywords[rlen] = 0;
rlen++;
}
// Now the quotient is in xwords, and the remainder is in ywords.
bool add_one = false;
if (rlen > 1 || ywords[0] != 0)
{ // Non-zero remainder i.e. in-exact quotient.
switch (rounding_mode)
{
case TRUNCATE:
break;
case CEILING:
if (qNegative == (rounding_mode == FLOOR))
add_one = true;
break;
case FLOOR:
if (qNegative == (rounding_mode == FLOOR))
add_one = true;
break;
case ROUND:
// int cmp = compare (remainder<<1, abs(y));
IntNum tmp = remainder == null ? new IntNum() : remainder;
tmp.set (ywords, rlen);
tmp = shift (tmp, 1);
if (yNegative)
tmp.setNegative();
int cmp = compare (tmp, y);
// Now cmp == compare(sign(y)*(remainder<<1), y)
if (yNegative)
cmp = -cmp;
add_one = (cmp == 1) || (cmp == 0 && (xwords[0]&1) != 0);
break;
}
}
if (quotient != null)
{
if (xwords[qlen-1] < 0)
{
xwords[qlen] = 0;
qlen++;
}
quotient.set (xwords, qlen);
if (qNegative)
{
if (add_one) // -(quotient + 1) == ~(quotient)
quotient.setInvert ();
else
quotient.setNegative ();
}
else if (add_one)
quotient.setAdd (1);
}
if (remainder != null)
{
// The remainder is by definition: X-Q*Y
remainder.set (ywords, rlen);
if (add_one)
{
// Subtract the remainder from Y:
// abs(R) = abs(Y) - abs(orig_rem) = -(abs(orig_rem) - abs(Y)).
IntNum tmp;
if (y.words == null)
{
tmp = remainder;
tmp.set(yNegative ? ywords[0] + y.ival : ywords[0] - y.ival);
}
else
tmp = IntNum.add(remainder, y, yNegative ? 1 : -1);
// Now tmp <= 0.
// In this case, abs(Q) = 1 + floor(abs(X)/abs(Y)).
// Hence, abs(Q*Y) > abs(X).
// So sign(remainder) = -sign(X).
if (xNegative)
remainder.setNegative(tmp);
else
remainder.set(tmp);
}
else
{
// If !add_one, then: abs(Q*Y) <= abs(X).
// So sign(remainder) = sign(X).
if (xNegative)
remainder.setNegative ();
}
}
}
public static IntNum abs(IntNum x)
{
return x.isNegative () ? neg (x) : x;
}
void setShiftRight(IntNum x, int count)
{
if (x.words == null)
set (count < 32 ? x.ival >> count : x.ival < 0 ? -1 : 0);
else if (count == 0)
set (x);
else
{
bool neg = x.isNegative ();
int word_count = count >> 5;
count &= 31;
int d_len = x.ival - word_count;
if (d_len <= 0)
set (neg ? -1 : 0);
else
{
if (words == null || words.Length < d_len)
realloc (d_len);
MPN.rshift0 (words, x.words, word_count, d_len, count);
ival = d_len;
if (neg)
words[d_len-1] |= -2 << (31 - count);
}
}
}
/** Return -1, 0, or 1, depending on which value is greater. */
public static int compare(IntNum x, long y)
{
long x_word;
if (x.words == null)
x_word = x.ival;
else
{
bool x_negative = x.isNegative ();
bool y_negative = y < 0;
if (x_negative != y_negative)
return x_negative ? -1 : 1;
int x_len = x.words == null ? 1 : x.ival;
if (x_len == 1)
x_word = x.words[0];
else if (x_len == 2)
x_word = x.longValue();
else // We assume x is canonicalized.
return x_negative ? -1 : 1;
}
return x_word < y ? -1 : x_word > y ? 1 : 0;
}
/** Return -1, 0, or 1, depending on which value is greater. */
public static int compare(IntNum x, IntNum y)
{
if (x.words == null && y.words == null)
return x.ival < y.ival ? -1 : x.ival > y.ival ? 1 : 0;
bool x_negative = x.isNegative ();
bool y_negative = y.isNegative ();
if (x_negative != y_negative)
return x_negative ? -1 : 1;
int x_len = x.words == null ? 1 : x.ival;
int y_len = y.words == null ? 1 : y.ival;
if (x_len != y_len) // We assume x and y are canonicalized.
return (x_len > y_len)!=x_negative ? 1 : -1;
return MPN.cmp (x.words, y.words, x_len);
}
public override Numeric power(IntNum y)
{
if (isOne())
return this;
if (isMinusOne())
return y.isOdd () ? this : IntNum.one ();
if (y.words == null && y.ival >= 0)
return power (this, y.ival);
if (isZero())
return y.isNegative () ? RatNum.infinity(-1) : (RatNum) this;
return base.power (y);
}
/** Return this raised to an integer power.
* Implemented by repeated squaring and multiplication.
* If y < 0, returns div_inv of the result. */
public virtual Numeric power(IntNum y)
{
if (y.isNegative ())
return power(IntNum.neg(y)).div_inv();
Numeric pow2 = this;
Numeric r = null;
for (;;) // for (i = 0; ; i++)
{
// pow2 == x**(2**i)
// prod = x**(sum(j=0..i-1, (y>>j)&1))
if (y.isOdd())
r = r == null ? pow2 : r.mul (pow2); // r *= pow2
y = IntNum.shift (y, -1);
if (y.isZero())
break;
// pow2 *= pow2;
pow2 = pow2.mul (pow2);
}
return r == null ? mul_ident() : r;
}
