public bool IsDefined(SymbolAtom sym)
{
if (IsDefinedHere(sym))
{
return(true);
}
if (Parent == null)
{
return(false);
}
return(Parent.IsDefined(sym));
}
public ISExpression Lookup(SymbolAtom sym)
{
if (Data.ContainsKey(sym))
{
return(Data[sym]);
}
if (Parent != null)
{
return(Parent.Lookup(sym));
}
return(null);
}
public bool Set(SymbolAtom sym, ISExpression sexpr)
{
if (IsDefinedHere(sym))
{
DefineHere(sym, sexpr);
return(true);
}
else if (Parent == null)
{
return(false);
}
else
{
return(Parent.Set(sym, sexpr));
}
}
public void DefineHere(SymbolAtom sym, ISExpression sexpr)
{
Data[sym] = sexpr;
}
public bool IsDefinedHere(SymbolAtom sym)
{
return(Data.ContainsKey(sym));
}