/// <summary>
/// Initializes a new instance of the <see cref="VariableExpression" /> class.
/// </summary>
/// <param name="expression">The string expression</param>
/// <param name="model">The model</param>
public VariableExpression(string expression, Model model)
{
this.expression = expression;
this.Object = model;
// Perform initial parsing.
this.fn = new ExpressionEvaluator();
this.fn.Parse(this.expression.Trim());
this.fn.Infix2Postfix();
}
/// <summary>
/// Return the value of the specified property as an object. The PropertyName
/// is relative to the RelativeTo argument (usually Plant).
/// Format:
/// [function(]VariableName[)]
/// Where:
/// function is optional and can be one of Sum, subtract, multiply, divide, max, min
/// VariableName is the name of a Plant variable. It can also include an array. Array can
/// have a filter inside of square brackets. Filter can be an array index (0 based)
/// or be the name of a class or base class.
/// e.g. Leaf.MinT
/// sum(Leaf.Leaves[].Live.Wt) - sums all live weights of all objects in leaves array.
/// subtract(Leaf.Leaves[].Live.Wt) - subtracts all live weights of all objects in leaves array.
/// Leaf.Leaves[1].Live.Wt - returns the live weight of the 2nd element of the leaves array.
/// sum(Leaf.Leaves[AboveGround].Live.Wt) - returns the live weight of the 2nd element of the leaves array.
/// </summary>
/// <param name="Expression">The expression.</param>
/// <param name="RelativeTo">The relative to.</param>
/// <returns></returns>
public static object Evaluate(string Expression, Model RelativeTo)
{
ExpressionEvaluator fn = new ExpressionEvaluator();
Parse(fn, Expression);
FillVariableNames(fn, RelativeTo);
Evaluate(fn);
if (fn.Results != null)
return fn.Results;
else
return fn.Result;
}
/// <summary>Parses the specified function.</summary>
/// <param name="fn">The function.</param>
/// <param name="ExpressionProperty">The expression property.</param>
private static void Parse(ExpressionEvaluator fn, string ExpressionProperty)
{
fn.Parse(ExpressionProperty.Trim());
fn.Infix2Postfix();
}
/// <summary>Fills the variable names.</summary>
/// <param name="fn">The function.</param>
/// <param name="RelativeTo">The relative to.</param>
/// <exception cref="System.Exception">Cannot find variable: + sym.m_name + in function: + RelativeTo.Name</exception>
private static void FillVariableNames(ExpressionEvaluator fn, Model RelativeTo)
{
ArrayList varUnfilled = fn.Variables;
ArrayList varFilled = new ArrayList();
Symbol symFilled;
foreach (Symbol sym in varUnfilled)
{
symFilled.m_name = sym.m_name;
symFilled.m_type = ExpressionType.Variable;
symFilled.m_values = null;
symFilled.m_value = 0;
object sometypeofobject = Apsim.Get(RelativeTo, sym.m_name.Trim());
if (sometypeofobject == null)
throw new Exception("Cannot find variable: " + sym.m_name + " in function: " + RelativeTo.Name);
symFilled.m_value = Convert.ToDouble(sometypeofobject);
varFilled.Add(symFilled);
}
fn.Variables = varFilled;
}
/// <summary>Evaluates the specified function.</summary>
/// <param name="fn">The function.</param>
/// <exception cref="System.Exception"></exception>
private static void Evaluate(ExpressionEvaluator fn)
{
fn.EvaluatePostfix();
if (fn.Error)
{
throw new Exception(fn.ErrorDescription);
}
}
