/// <summary>
/// evaluation of this polynomial at a given point
/// </summary>
/// <param name="a">A.</param>
/// <returns>evaluation of this polynomial at a given point</returns>
internal int evaluateAt(int a)
{
int result = 0;
if (a == 0)
{
// Just return the x^0 coefficient
return(getCoefficient(0));
}
int size = coefficients.Length;
if (a == 1)
{
// Just the sum of the coefficients
foreach (var coefficient in coefficients)
{
result = GenericGF.addOrSubtract(result, coefficient);
}
return(result);
}
result = coefficients[0];
for (int i = 1; i < size; i++)
{
result = GenericGF.addOrSubtract(field.multiply(a, result), coefficients[i]);
}
return(result);
}
internal GenericGFPoly multiply(GenericGFPoly other)
{
if (!field.Equals(other.field))
{
throw new ArgumentException("GenericGFPolys do not have same GenericGF field");
}
if (isZero || other.isZero)
{
return(field.Zero);
}
int[] aCoefficients = this.coefficients;
int aLength = aCoefficients.Length;
int[] bCoefficients = other.coefficients;
int bLength = bCoefficients.Length;
int[] product = new int[aLength + bLength - 1];
for (int i = 0; i < aLength; i++)
{
int aCoeff = aCoefficients[i];
for (int j = 0; j < bLength; j++)
{
product[i + j] = GenericGF.addOrSubtract(product[i + j],
field.multiply(aCoeff, bCoefficients[j]));
}
}
return(new GenericGFPoly(field, product));
}