public Symbol Evaluate(Symbol symbol)
{
if (symbol is Expression expression && expression.Count > 0)
{
Expression.Builder builder = new Expression.Builder(expression);
for (int i = 0; i < builder.Count; i++)
{
if (builder.Arguments[i] is Expression)
{
builder.Arguments[i] = Evaluate(builder[i]);
}
}
if (Evaluators.TryGetValue(builder[0], out var evaluator))
{
symbol = evaluator.Evaluate(builder.Build(), this);
}
}
History.Insert(0, symbol);
for (int i = 0; i < Math.Min(History.Count, 10); i++)
{
Variable[Atom.OfHistory(i)] = History[i];
}
return(symbol);
}
public static Symbol Parse(string value)
{
Stack <Expression.Builder> groupings = new Stack <Expression.Builder>();
var root = new Expression.Builder();
groupings.Push(root);
for (int i = 0; i < value.Length;)
{
switch (value[i])
{
case '(':
var group = new Expression.Builder();
groupings.Peek().Arguments.Add(group);
groupings.Push(group);
i++;
break;
case ')':
groupings.Pop();
i++;
break;
default:
if (value[i] == ',' || char.IsWhiteSpace(value[i]))
{
i++;
}
else if (value[i] == '"')
{
var end = value.IndexOfAny(new char[] { '"' }, ++i);
var text = value.Substring(i, end - i);
groupings.Peek().Arguments.Add(new Text(text));
i = end + 1;
}
else if (char.IsNumber(value[i]))
{
var end = value.IndexOfAny(new char[] { ' ', ',', ')' }, i);
if (end == -1)
{
end = value.Length;
}
var number = value.Substring(i, end - i);
groupings.Peek().Arguments.Add(new Numeric(double.Parse(number)));
i = end;
}
else
{
var end = value.IndexOfAny(new char[] { ' ', ',', ')' }, i);
if (end == -1)
{
end = value.Length;
}
var text = value.Substring(i, end - i);
groupings.Peek().Arguments.Add(Atom.OfName(text));
i = end;
}
break;
}
}
if (root.Arguments.Count > 1)
{
return(root.Build());
}
else if (root.Arguments.Count == 1)
{
return(root.Build()[0]);
}
return(Expression.Empty);
}
