public BigInteger ModPow(int power, BigInteger mod)
{
if (power == 0)
{
return(One);
}
if (power < 0)
{
throw new ArgumentOutOfRangeException("NonNegativePower");
}
BigInteger factor = this;
BigInteger result = One; //!!! want a mutable here for efficiency
while (power != 0)
{
if ((power & 1) != 0)
{
result = result * factor;
result = result % mod; //!!! should do all in one step
}
factor = factor.Square();
power >>= 1;
}
return(result);
}
public BigInteger Power(int exp)
{
if (exp == 0)
{
return(One);
}
if (exp < 0)
{
throw new ArgumentOutOfRangeException("NonNegativePower");
}
BigInteger factor = this;
BigInteger result = One; //!!! want a mutable here for efficiency
while (exp != 0)
{
if ((exp & 1) != 0)
{
result = result * factor;
}
if (exp == 1)
{
break; // avoid costly factor.square()
}
factor = factor.Square();
exp >>= 1;
}
return(result);
}