private long CalcPossibilitiesOfDepth(CFGExpressionGrammar grammar, int depth)
{
long pos = 0;
var terminalSymbols = grammar.AllowedSymbols.Where(x => x.MaximumArity <= 0 && !(x is GroupSymbol));
var nonterminalSymbols = grammar.AllowedSymbols.Where(x => x.MinimumArity > 0 && !(x is ProgramRootSymbol) && !(x is StartSymbol) && !(x is Defun) && (x is CFGProduction || !(x is CFGSymbol)));
var startSymbols = grammar.GetAllowedChildSymbols(grammar.StartSymbol, 0);
foreach (var symbol in nonterminalSymbols)
{
depthPerSymbolTrees.Add(symbol, new Dictionary <int, int>());
}
for (int i = 2; i < depth + 1; i++)
{
foreach (var ntSymbol in nonterminalSymbols)
{
int symPos = 1;
for (int j = 0; j < ntSymbol.MaximumArity; j++)
{
int symbolArityPos = 0;
foreach (var childSymbol in grammar.GetAllowedChildSymbols(ntSymbol, j))
{
if (terminalSymbols.Contains(childSymbol))
{
symbolArityPos++;
}
else
{
if (depthPerSymbolTrees[childSymbol].ContainsKey(i - 1))
{
symbolArityPos += depthPerSymbolTrees[childSymbol][i - 1];
}
}
}
symPos *= symbolArityPos;
}
depthPerSymbolTrees[ntSymbol].Add(i, symPos);
}
}
foreach (var sy in startSymbols)
{
if (depthPerSymbolTrees.ContainsKey(sy))
{
pos += depthPerSymbolTrees[sy].ContainsKey(depth) ? depthPerSymbolTrees[sy][depth] : 0;
}
else
{
pos += 1;
}
}
return(pos);
}
private ISymbol GetSymbol(CFGExpressionGrammar grammar, string name)
{
return(grammar.Symbols.First(x => x.Name == name));
}
