public static OneNode NewNode(ref string st, ref int pos)
{
OneNode res = null;
while (pos < st.Length && st[pos] == ' ')
{
++pos;
}
//MessageBox.Show("In ONENODE, '" + st[pos] + "'");
if (pos < st.Length)
{
if (Char.IsLower(st[pos]))
{
res = new VarNode("");
}
else
if (Char.IsDigit(st[pos]))
{
res = new IntNode(0);
}
else
if (st[pos] == '(')
{
res = new SignNode(Sign.empty);
}
}
if (res != null && !res.LoadNodeFromString(ref st, ref pos))
{
res = null;
}
return(res);
}
bool TryClear(ref OneNode R, ref int count)
{
bool res = true;
if (R != null)
{
OneNode l = R.left;
OneNode r = R.right;
if (Root is SignNode)
{
if (l == null || r == null)
{
return(false);
}
Sign s = ((SignNode)R).Sign;
// MessageBox.Show("Here, s = " + s.ToString());
if (l is IntNode && r is IntNode)
{
int left = ((IntNode)l).Finfo;
int right = ((IntNode)r).Finfo;
switch (s)
{
case Sign.mult:
R = new IntNode(left * right);
++count;
break;
case Sign.add:
R = new IntNode(left + right);
++count;
break;
case Sign.divide:
if (right == 0)
{
return(false);
}
else
{
R = new IntNode(left / right);
}
++count;
break;
case Sign.subst:
R = new IntNode(left - right);
++count;
break;
default: return(false);
}
}
else
{
switch (s)
{
case Sign.add:
if (l is IntNode && ((IntNode)l).Finfo == 0)
{
R = R.right;
++count;
TryClear(ref R, ref count);
}
else
if (r is IntNode && ((IntNode)r).Finfo == 0)
{
R = R.left;
++count;
TryClear(ref R, ref count);
}
else
{
TryClear(ref R.left, ref count);
TryClear(ref R.right, ref count);
}
break;
case Sign.divide:
if (l is IntNode && ((IntNode)l).Finfo == 0)
{
R = new IntNode(0);
++count;
}
else
if (r is IntNode)
{
if (((IntNode)r).Finfo == 0)
{
return(false);
}
else
if (((IntNode)r).Finfo == 1)
{
R = R.left;
++count;
TryClear(ref R, ref count);
}
}
else
{
TryClear(ref R.left, ref count);
TryClear(ref R.right, ref count);
}
break;
case Sign.mult:
if (l is IntNode)
{
if (((IntNode)l).Finfo == 0)
{
++count;
R = new IntNode(0);
}
else
if (((IntNode)l).Finfo == 1)
{
R = R.right;
++count;
TryClear(ref R, ref count);
}
}
else
if (r is IntNode)
{
if (((IntNode)r).Finfo == 0)
{
R = new IntNode(0);
++count;
}
else
if (((IntNode)r).Finfo == 1)
{
R = R.left;
++count;
TryClear(ref R, ref count);
}
}
else
{
TryClear(ref R.left, ref count);
TryClear(ref R.right, ref count);
}
break;
case Sign.subst:
if (r is IntNode && ((IntNode)r).Finfo == 0)
{
R = R.left;
++count;
TryClear(ref R, ref count);
}
else
{
TryClear(ref R.left, ref count);
TryClear(ref R.right, ref count);
}
break;
default: return(false);
}
}
}
}
return(res);
}
public override OneNode Copy()
{
IntNode result = new IntNode(this.Finfo);
return(result);
}