public void TestDegToGrad(double deg, double expectedGrad)
{
Number result = NumberMath.DegToGrad(deg);
AreEqual(expectedGrad, result, 1E-9);
}
/// <summary>
/// Integrates the expression with Simpson algorithm
/// </summary>
/// <param name="expression">Expression to integrate</param>
/// <param name="var">Integrate by which expression</param>
/// <param name="from">Start value</param>
/// <param name="to">End value</param>
/// <param name="steps">Number of steps</param>
/// <returns>Integration result</returns>
public static INumber Integrate(this IExpression expression, string var, INumber from, INumber to, int steps = 2048)
{
Number?_from = from as Number;
Number?_to = to as Number;
if (_from == null || _to == null)
{
throw new ExpressionEngineException();
}
if (_to < _from)
{
throw new ArgumentException(Resources.IntegrateErrorRange);
}
if (steps < 2 || (steps % 2 == 1))
{
throw new ArgumentException(Resources.InvalidSteps);
}
var flatExpression = expression.Flatten();
var vars = flatExpression.FirstOrDefault(e => e.Variables != null)?.Variables;
bool trigonometric = flatExpression.Any(e => IsTrigonometricNode(e));
if (trigonometric)
{
switch (NumberMath.AngleMode)
{
case AngleMode.Deg:
_from = NumberMath.DegToRad(_from);
_to = NumberMath.DegToRad(_to);
break;
case AngleMode.Grad:
_from = NumberMath.DegToGrad(_from);
_to = NumberMath.DegToGrad(_to);
break;
}
}
if (vars == null)
{
throw new InvalidOperationException(Resources.NoVariables);
}
if (string.IsNullOrEmpty(var))
{
throw new ArgumentNullException(nameof(var));
}
AngleMode old = NumberMath.AngleMode;
NumberMath.AngleMode = AngleMode.Rad;
Number h = (_to - _from) / steps;
Number x = _from + h;
Number s = 0.0;
for (int i = 1; i < steps / 2; i++)
{
vars[var] = x;
Number Fx = (expression.Evaluate() as Number) !;
vars[var] = x + h;
Number Fx2 = (expression.Evaluate() as Number) !;
s = s + (2 * Fx) + Fx2;
x += 2 * h;
}
vars[var] = from;
Number Fxa = (expression.Evaluate() as Number) !;
vars[var] = to;
Number Fxb = (expression.Evaluate() as Number) !;
vars[var] = _to - h;
Number Fxhb = (expression.Evaluate() as Number) !;
Number result = (h / 3) * ((2 * s) + Fxa + Fxb + (4 * Fxhb));
NumberMath.AngleMode = old;
return(NumberMath.Round(result, 15));
}
