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Polynomial: add static Zero to get the zero-polynomial

pull/601/head
Christoph Ruegg 8 years ago
parent
9f8da8b00c
commit
6c0bc89342
2 changed files with 45 additions and 8 deletions
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  1. 10
      src/Numerics.Tests/PolynomialTests.cs
  2. 43
      src/Numerics/Polynomial.cs

10
src/Numerics.Tests/PolynomialTests.cs
View File

@ -218,25 +218,25 @@ namespace MathNet.Numerics.UnitTests
Assert.Throws(typeof(DivideByZeroException), () =>
{
var p1 = new Polynomial(1.0d);
var p2 = new Polynomial();
var p2 = Polynomial.Zero;
GC.KeepAlive(Polynomial.DivideRemainder(p1, p2));
});
Assert.DoesNotThrow(() =>
{
var p1 = new Polynomial();
var p1 = Polynomial.Zero;
var p2 = new Polynomial(1.0d);
GC.KeepAlive(Polynomial.DivideRemainder(p1, p2));
});
Assert.Throws(typeof(DivideByZeroException), () =>
{
var p1 = new Polynomial();
var p2 = new Polynomial();
var p1 = Polynomial.Zero;
var p2 = Polynomial.Zero;
GC.KeepAlive(Polynomial.DivideRemainder(p1, p2));
});
Assert.Throws(typeof(DivideByZeroException), () =>
{
var p1 = new Polynomial(1.0d);
var p2 = new Polynomial();
var p2 = Polynomial.Zero;
GC.KeepAlive(Polynomial.DivideRemainder(p1, p2));
});
}

43
src/Numerics/Polynomial.cs
View File

@ -47,6 +47,7 @@ namespace MathNet.Numerics
/// <summary>
/// Create a zero-polynomial with a coefficient array of the given length.
/// An array of length N can support polynomials of a degree of at most N-1.
/// </summary>
/// <param name="n">Length of the coefficient array</param>
public Polynomial(int n)
@ -64,7 +65,11 @@ namespace MathNet.Numerics
/// </summary>
public Polynomial()
{
#if NET40
Coefficients = new double[0];
#else
Coefficients = Array.Empty<double>();
#endif
}
/// <summary>
@ -109,6 +114,8 @@ namespace MathNet.Numerics
return -1;
}
public static Polynomial Zero => new Polynomial();
/// <summary>
/// Least-Squares fitting the points (x,y) to a k-order polynomial y : x -> p0 + p1*x + p2*x^2 + ... + pk*x^k
/// </summary>
@ -119,6 +126,7 @@ namespace MathNet.Numerics
}
#region Evaluation
/// <summary>
/// Evaluate a polynomial at point x.
/// Coefficients are ordered by power with power k at index k.
@ -211,9 +219,11 @@ namespace MathNet.Numerics
{
return z.Select(Evaluate);
}
#endregion
#region Calculus
public Polynomial Differentiate()
{
int n = Degree;
@ -221,10 +231,11 @@ namespace MathNet.Numerics
{
return this;
}
if (n == 0)
{
// Zero
return new Polynomial();
return Zero;
}
var c = new double[n];
@ -252,9 +263,11 @@ namespace MathNet.Numerics
return new Polynomial(c);
}
#endregion
#region Linear Algebra
/// <summary>
/// Calculates the complex roots of the Polynomial by eigenvalue decomposition
/// </summary>
@ -304,9 +317,11 @@ namespace MathNet.Numerics
return A;
}
#endregion
#region Arithmetic Operations
/// <summary>
/// Addition of two Polynomials (point-wise).
/// </summary>
@ -538,14 +553,14 @@ namespace MathNet.Numerics
if (bDegree == 0)
{
// division by scalar
return Tuple.Create(Divide(a, b.Coefficients[0]), new Polynomial());
return Tuple.Create(Divide(a, b.Coefficients[0]), Zero);
}
if (aDegree < bDegree)
{
// denominator degree higher than nominator degree
// quotient always be 0 and return c1 as remainder
return Tuple.Create(new Polynomial(), a);
return Tuple.Create(Zero, a);
}
var c1 = a.Coefficients.ToArray();
@ -567,6 +582,7 @@ namespace MathNet.Numerics
{
c1[k] -= c22[k - i] * v;
}
i--;
j--;
}
@ -588,9 +604,11 @@ namespace MathNet.Numerics
return Tuple.Create(new Polynomial(quo), new Polynomial(rem));
}
#endregion
#region Arithmetic Pointwise Operations
/// <summary>
/// Point-wise division of two Polynomials
/// </summary>
@ -639,9 +657,11 @@ namespace MathNet.Numerics
return new Polynomial(result);
}
#endregion
#region Arithmetic Instance Methods (forwarders)
/// <summary>
/// Division of two polynomials returning the quotient-with-remainder of the two polynomials given
/// </summary>
@ -651,9 +671,11 @@ namespace MathNet.Numerics
{
return DivideRemainder(this, b);
}
#endregion
#region Arithmetic Operator Overloads (forwarders)
/// <summary>
/// Addition of two Polynomials (piecewise)
/// </summary>
@ -773,9 +795,11 @@ namespace MathNet.Numerics
{
return Divide(a, k);
}
#endregion
#region ToString
/// <summary>
/// Format the polynomial in ascending order, e.g. "4.3 + 2.0x^2 - x^3".
/// </summary>
@ -807,6 +831,7 @@ namespace MathNet.Numerics
{
return ToStringDescending(format, CultureInfo.CurrentCulture);
}
/// <summary>
/// Format the polynomial in ascending order, e.g. "4.3 + 2.0x^2 - x^3".
/// </summary>
@ -850,6 +875,7 @@ namespace MathNet.Numerics
{
sb.Append(VariableName);
}
if (i > 1)
{
sb.Append("^");
@ -870,10 +896,12 @@ namespace MathNet.Numerics
sb.Append(" + ");
sb.Append(c.ToString(format, formatProvider));
}
if (i > 0)
{
sb.Append(VariableName);
}
if (i > 1)
{
sb.Append("^");
@ -912,6 +940,7 @@ namespace MathNet.Numerics
{
sb.Append(VariableName);
}
if (i > 1)
{
sb.Append("^");
@ -932,10 +961,12 @@ namespace MathNet.Numerics
sb.Append(" + ");
sb.Append(c.ToString(format, formatProvider));
}
if (i > 0)
{
sb.Append(VariableName);
}
if (i > 1)
{
sb.Append("^");
@ -946,9 +977,11 @@ namespace MathNet.Numerics
return sb.ToString();
}
#endregion
#region Equality
public bool Equals(Polynomial other)
{
if (ReferenceEquals(null, other)) return false;
@ -990,11 +1023,14 @@ namespace MathNet.Numerics
hash = hash * 31 + Coefficients[i].GetHashCode();
}
}
return hash;
}
#endregion
#region Clone
public Polynomial Clone()
{
int degree = EvaluateDegree(Coefficients);
@ -1015,6 +1051,7 @@ namespace MathNet.Numerics
return Clone();
}
#endif
#endregion
}
}

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