public static Signal PolynomialDivision(Signal numerator, Signal denominator, Signal variable, out Signal remainder)
{
Signal[] R = PolynomialCoefficients(numerator, variable);
Signal[] B = PolynomialCoefficients(denominator, variable);
int degB = B.Length - 1;
Signal lcB = B[degB];
Signal[] Q = new Signal[R.Length - degB];
for (int delta = R.Length - 1 - degB; delta >= 0; delta--)
{
int degR = degB + delta;
if (Std.IsConstantAdditiveIdentity(R[degR]))
{
Q[delta] = R[degR];
continue;
}
Signal T = Std.Divide(R[degR], lcB);
Q[delta] = T;
R[degB + delta] = IntegerValue.ConstantZero;
for (int i = delta; i < degB + delta; i++)
{
R[i] = Std.Subtract(R[i], Std.Multiply(B[i - delta], T));
}
}
remainder = ConstructPolynomial(variable, R);
return(ConstructPolynomial(variable, Q));
}
/// <summary>
/// Evaluates the degree of the single-variable monomial <see cref="signal"/>.
/// </summary>
/// <returns>
/// <see cref="UndefinedSymbol"/> if <see cref="signal"/> is not a single-variable monomial.
/// <see cref="NegativeInfinitySymbol"/> if <see cref="signal"/> is zero.
/// Otherwise an <see cref="IntegerValue"/> representing the asked degree.
/// </returns>
/// <remarks><see cref="signal"/> is assumed to be automatic simplified.</remarks>
public static IValueStructure MonomialDegree(Signal signal, Signal variable)
{
if (signal == null)
{
throw new ArgumentNullException("signal");
}
if (Std.IsConstantAdditiveIdentity(signal))
{
return(NegativeInfinitySymbol.Instance);
}
if (Std.IsAlwaysRational(signal))
{
return(IntegerValue.Zero);
}
if (signal.IsDrivenByPortEntity("Multiply", "Std") && signal.DrivenByPort.InputSignalCount == 2 && Std.IsAlwaysRational(signal.DrivenByPort.InputSignals[0]))
{
signal = signal.DrivenByPort.InputSignals[1];
}
if (signal.Equals(variable))
{
return(IntegerValue.One);
}
if (signal.IsDrivenByPortEntity("Power", "Std"))
{
Signal b = signal.DrivenByPort.InputSignals[0];
Signal e = signal.DrivenByPort.InputSignals[1];
if (b.Equals(variable) && Std.IsAlwaysPositiveInteger(e))
{
return(e.Value);
}
}
return(UndefinedSymbol.Instance);
}
public static IValueStructure MonomialDegree(Signal signal, Signal[] generalizedVariables)
{
if (Std.IsConstantAdditiveIdentity(signal))
{
return(NegativeInfinitySymbol.Instance);
}
if (Array.Exists <Signal>(generalizedVariables, signal.Equals))
{
return(IntegerValue.One);
}
if (!Array.Exists <Signal>(generalizedVariables, signal.DependsOn))
{
return(IntegerValue.Zero);
}
ISignalSet factors;
long deg = 0;
if (signal.IsDrivenByPortEntity("Multiply", "Std"))
{
factors = signal.DrivenByPort.InputSignals;
}
else
{
factors = new SignalSet(signal);
}
for (int i = 0; i < factors.Count; i++)
{
if (Array.Exists <Signal>(generalizedVariables, factors[i].Equals))
{
deg++;
}
else if (factors[i].IsDrivenByPortEntity("Power", "Std"))
{
Signal b = signal.DrivenByPort.InputSignals[0];
Signal e = signal.DrivenByPort.InputSignals[1];
IntegerValue v;
if (Array.Exists <Signal>(generalizedVariables, b.Equals) && (v = e.Value as IntegerValue) != null && v.Value > 0)
{
deg += v.Value;
}
}
}
return(new IntegerValue(deg));
}
/// <summary>
/// Returns the coefficient factor in the monomial <see cref="signal"/>
/// </summary>
/// <returns>
/// Constant UndefinedSymbol if <see cref="signal"/> is not a single-variable monomial.
/// Otherwise the coefficient factor of the term.
/// </returns>
/// </returns>
/// <remarks><see cref="signal"/> is assumed to be automatic simplified.</remarks>
public static Signal MonomialCoefficient(Signal signal, Signal variable, out IValueStructure degree)
{
if (signal == null)
{
throw new ArgumentNullException("signal");
}
if (Std.IsConstantAdditiveIdentity(signal))
{
degree = NegativeInfinitySymbol.Instance;
return(signal);
}
if (Std.IsAlwaysRational(signal))
{
degree = IntegerValue.Zero;
return(signal);
}
Signal coeff = IntegerValue.ConstantOne;
if (signal.IsDrivenByPortEntity("Multiply", "Std") && signal.DrivenByPort.InputSignalCount == 2 && Std.IsAlwaysRational(signal.DrivenByPort.InputSignals[0]))
{
coeff = signal.DrivenByPort.InputSignals[0];
signal = signal.DrivenByPort.InputSignals[1];
}
if (signal.Equals(variable))
{
degree = IntegerValue.One;
return(coeff);
}
if (signal.IsDrivenByPortEntity("Power", "Std"))
{
Signal b = signal.DrivenByPort.InputSignals[0];
Signal e = signal.DrivenByPort.InputSignals[1];
if (b.Equals(variable) && Std.IsAlwaysPositiveInteger(e))
{
degree = e.Value;
return(coeff);
}
}
degree = UndefinedSymbol.Instance;
return(UndefinedSymbol.Constant);
}
public static Signal ConstructPolynomial(Signal variable, params Signal[] coefficients)
{
Signal[] summands = new Signal[coefficients.Length];
for (int i = 0; i < summands.Length; i++)
{
Signal coeff = coefficients[i];
if (Std.IsConstantAdditiveIdentity(coeff))
{
summands[i] = coeff;
continue;
}
if (i == 0)
{
summands[0] = coeff;
}
else if (i == 1)
{
if (Std.IsConstantMultiplicativeIdentity(coeff))
{
summands[1] = variable;
}
else
{
summands[1] = StdBuilder.Multiply(coeff, variable);
}
}
else
{
if (Std.IsConstantMultiplicativeIdentity(coeff))
{
summands[i] = StdBuilder.Power(variable, IntegerValue.Constant(i));
}
else
{
summands[i] = StdBuilder.Multiply(coeff, StdBuilder.Power(variable, IntegerValue.Constant(i)));
}
}
}
return(Std.Add(summands));
}