public int PostfixEvalSpanStack()
{
Span <Token> span = new Token[100];
var stack = span.AsStack();
foreach (var token in tokens)
{
switch (token)
{
case Operand t:
stack.Push(t);
break;
case Operator o:
var a = stack.Pop() as Operand;
var b = stack.Pop() as Operand;
var result = o.Calc(a.Value, b.Value);
stack.Push(new Operand(result));
break;
}
}
return((stack.Pop() as Operand).Value);
}
