/// <summary>
/// Given a list of arguments, it looks at the types and tries to find out which function
/// in this list is the best match.
/// </summary>
/// <param name="list"></param>
/// <param name="funcs"></param>
/// <returns></returns>
public FunctionValue FindBestMatch(List <FunctionValue> list, HeronValue[] args)
{
// Each iteration removes candidates. This list holds all of the matches
// Necessary, because removing items from a list while we iterate it is hard.
List <FunctionValue> tmp = new List <FunctionValue>(list);
for (int pos = 0; pos < args.Length; ++pos)
{
// On each iteration, update the main list, to only contain the remaining items
list = new List <FunctionValue>(tmp);
HeronValue arg = args[pos];
HeronType argType;
if (arg is AnyValue)
{
argType = (arg as AnyValue).GetHeldType();
}
else
{
argType = arg.Type;
}
for (int i = 0; i < list.Count; ++i)
{
FunctionValue fo = list[i];
HeronType formalType = fo.GetFormalType(pos);
if (!formalType.Equals(argType))
{
tmp.Remove(fo);
}
}
if (tmp.Count == 0)
{
throw new Exception("Could not resolve function " + name + " no function matches perfectly");
}
// We found a single best match
if (tmp.Count == 1)
{
return(tmp[0]);
}
}
Debug.Assert(tmp.Count > 1);
// There are multiple functions
// Choose the function which is the most derived type.
// This is a pretty awful hack to make up for a bad design.
int n = 0;
FunctionValue best = null;
foreach (FunctionValue fv in list)
{
int depth = fv.GetDefn().parent.GetHierarchyDepth();
if (depth > n)
{
n = depth;
best = fv;
}
else if (depth == n)
{
// Ambiguous match at this depth.
best = null;
}
}
if (best == null)
{
throw new Exception("Ambiguous function match");
}
return(best);
}