static void applyOperator(OpToken t, ref Stack <NumToken> nums)
{
if (t.type == OpType.LP || t.type == OpType.RP)
{
Console.WriteLine("Parenthesis mismatch");
return;
}
try
{
double op2 = nums.Pop().value;
double op1 = nums.Pop().value;
switch (t.type)
{
//last param of NumToken doesn't matter for any of them because they are not parsed from the string
case OpType.ADD:
nums.Push(new NumToken(op1 + op2, -1));
break;
case OpType.SUB:
nums.Push(new NumToken(op1 - op2, -1));
break;
case OpType.MUL:
nums.Push(new NumToken(op1 * op2, -1));
break;
case OpType.DIV:
nums.Push(new NumToken(op1 / op2, -1));
break;
case OpType.EXP:
nums.Push(new NumToken(Math.Pow(op1, op2), -1));
break;
case OpType.MOD:
nums.Push(new NumToken(op1 % op2, -1));
break;
case OpType.LSHIFT:
nums.Push(new NumToken((int)op1 << (int)op2, -1));
break;
case OpType.RSHIFT:
nums.Push(new NumToken((int)op1 >> (int)op2, -1));
break;
}
}
catch (Exception)
{
Console.WriteLine("Encountered exception, please check your syntax");
}
}
static void Main(string[] args)
{
Console.WriteLine("Input an expression. Note that _ is the negative sign. Use of >> << is rounded.");
string exp = Console.ReadLine();
exp = exp.Replace(" ", ""); //strip spaces
Stack <NumToken> nums = new Stack <NumToken>(); //number stack
Stack <OpToken> ops = new Stack <OpToken>(); //operator stack
for (int i = 0; i < exp.Length;) //increments of i will be determined based off whether it is a number or an operator
{
Token k = null;
try
{
k = getNextToken(exp, i);
}
catch (Exception)
{
Console.WriteLine("Error parsing token.");
break;
}
if (k is NumToken)
{
NumToken nt = (NumToken)k;
nums.Push(nt);
i += nt.length;
}
else if (k is OpToken)
{
OpToken x = (OpToken)k;
OpToken y = ops.Count > 0 ? ops.Peek() : null;
if (y == null || x.type == OpType.LP) //if stack has nothing in it yet, or if the token is a (, push it on stack, no evaluation
{
ops.Push(x);
}
else
{
if (x.type == OpType.RP) //if the current token is a ), unwind the stack until a ( is encountered
{
OpToken alpha = null;
while ((alpha = ops.Pop()).type != OpType.LP)
{
applyOperator(alpha, ref nums);
}
}
else
{
//apply operator if the current token is <= in precedence than the one on the top of the stack (< if right associative)
//parenthesis must be the smallest number so no other token will cause it to be applied
while ((x.leftasso && x.precedence <= y.precedence) || (!x.leftasso && x.precedence < y.precedence))
{
ops.Pop(); //pop y off, we're applying it
applyOperator(y, ref nums);
if (ops.Count == 0)
{
break;
}
y = ops.Peek(); //look at the next operator on stack in case it can be applied as well
}
ops.Push(x);
}
}
i += x.length;
}
}
//unwind remaining operators
while (ops.Count > 0)
{
OpToken y = ops.Pop();
applyOperator(y, ref nums);
}
if (nums.Count > 0)
{
Console.WriteLine(exp + " = " + nums.Pop().value);
}
else
{
Console.WriteLine("No result.");
}
Console.WriteLine("Press any key to exit.");
Console.ReadKey(false);
}
static void applyOperator(OpToken t, ref Stack<NumToken> nums)
{
if (t.type == OpType.LP || t.type == OpType.RP)
{
Console.WriteLine("Parenthesis mismatch");
return;
}
try
{
double op2 = nums.Pop().value;
double op1 = nums.Pop().value;
switch (t.type)
{
//last param of NumToken doesn't matter for any of them because they are not parsed from the string
case OpType.ADD:
nums.Push(new NumToken(op1 + op2, -1));
break;
case OpType.SUB:
nums.Push(new NumToken(op1 - op2, -1));
break;
case OpType.MUL:
nums.Push(new NumToken(op1 * op2, -1));
break;
case OpType.DIV:
nums.Push(new NumToken(op1 / op2, -1));
break;
case OpType.EXP:
nums.Push(new NumToken(Math.Pow(op1, op2), -1));
break;
case OpType.MOD:
nums.Push(new NumToken(op1 % op2, -1));
break;
case OpType.LSHIFT:
nums.Push(new NumToken((int)op1 << (int)op2, -1));
break;
case OpType.RSHIFT:
nums.Push(new NumToken((int)op1 >> (int)op2, -1));
break;
}
}
catch (Exception)
{
Console.WriteLine("Encountered exception, please check your syntax");
}
}