private Expression CompileIterationSum(int lambdaLevel)
{
PushPosition();
Move();
SkipPunctuation("(");
List <IterationSumVariable> variables = new List <IterationSumVariable>();
Expression body;
while (true)
{
bool isVariable;
PushPosition();
Move();
isVariable = IsPunctuationOf(":");
Pos = PeekPos();
if (isVariable)
{
if (!IsWord)
{
ThrowException("Expecting iteration variable name.");
}
string variableName = GetWord();
Move();
SkipPunctuation(":");
Expression from = Compile(lambdaLevel);
SkipPunctuation("->");
Expression to = Compile(lambdaLevel);
SkipPunctuation(",");
variables.Add(new IterationSumVariable()
{
From = from, To = to, Name = variableName
});
}
else
{
body = Compile(lambdaLevel);
SkipPunctuation(")");
break;
}
}
Expression result = new IterationSumExpression(variables.ToArray(), body, PeekPos(), Pos);
PopPosition();
return(result);
}
private void CheckIterationSumExpression(IterationSumExpression e, TypeCheckingContext context)
{
foreach (IterationSumVariable variable in e.Variables)
{
PerformTypeChecking(variable.From, context);
PerformTypeChecking(variable.To, context);
if (!Types.IsNumberType(variable.From.Type))
{
context.ErrorProvider.ThrowException(string.Format("Start value of {0} is not number.", variable.Name), e);
}
if (!Types.IsNumberType(variable.To.Type))
{
context.ErrorProvider.ThrowException(string.Format("End value of {1} is not number.", variable.Name), e);
}
context.VariableContext.Set(variable.Name, 0);
}
PerformTypeChecking(e.Body, context);
foreach (IterationSumVariable variable in e.Variables)
{
context.VariableContext.Remove(variable.Name);
}
if (!Types.IsNumberType(e.Body.Type))
{
context.ErrorProvider.ThrowException("Can only perform iteration sum on an expression of number type.", e);
}
e.Type = typeof(double);
}
private object EvaluateIterationSumExpression(IterationSumExpression e, VariableContext context)
{
int[] values = new int[e.Variables.Length];
int[] fromValues = new int[e.Variables.Length];
int[] toValues = new int[e.Variables.Length];
int index = 0;
foreach (IterationSumVariable variable in e.Variables)
{
if (context.HasVariable(variable.Name))
{
throw new Exception(string.Format("Iteration variable {0} is already in use.", variable.Name));
}
fromValues[index] = Types.ConvertValue <int>(Evaluate(variable.From, context));
toValues[index] = Types.ConvertValue <int>(Evaluate(variable.To, context));
context.Set(variable.Name, fromValues[index]);
values[index] = fromValues[index];
index++;
}
double sum = 0;
while (true)
{
double value = Types.ConvertValue <double>(Evaluate(e.Body, context));;
if (!double.IsNaN(value))
{
sum += value;
}
if (!IncreaseIterationValues(values, fromValues, toValues))
{
break;
}
else
{
for (int i = 0; i <= e.Variables.Length - 1; i++)
{
context.Set(e.Variables[i].Name, values[i]);
}
}
}
foreach (IterationSumVariable variable in e.Variables)
{
context.Remove(variable.Name);
}
return(sum);
}
