Graphic Calculator

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Collections;

namespace Graficadora
{
    public partial class Calculadora : Form
    {
        public Stack p = new Stack();
        public int clear = 0;
        public double mem;
        public Calculadora()
        {
            InitializeComponent();
        }
        public int prioridad(string c)
        {
            if ((c == "+") || (c == "-"))
                return 0;
            if ((c == "*") || (c == "/"))
                return 1;
            if (c == "^")
                return 2;
            if ((c == "Log") || (c == "Sen") || (c == "Cos") || (c == "Tan") || (c == "Exp"))
                return 3;
            return -1;
        }

        public bool operador(string o)
        {
            if (char.IsDigit(o, 0) || o == "x")
                return false;

            if (char.IsLetter(o, 0))
                return true;
            return true;
        }

        public string[] postfijo(string ecuacion)
        {
            string[] infijo = new string[20];
            int l = ecuacion.Length;
            int j; int k = 0; int i;
            string c; string tmp = "";
            string t = "(";
            for (i = 0; i < l; i++)
            {
                c = ecuacion[i].ToString();
                int band = 0;
                int band2 = 0;
                int band3 = 0;
                //Operando
                if (char.IsDigit(c, 0) || c == "x")
                {
                    j = i;
                    if (j < l)
                    {
                        while (char.IsDigit(ecuacion, j) || ecuacion[j].ToString() == ".")
                        {
                            infijo[k] = infijo[k] + ecuacion[j].ToString();
                            j++;
                            band++;
                            if (j == l)
                            {
                                break;
                            }
                        }
                    }
                    if (band > 0)
                    {
                        k++;
                        j--;
                    }
                    if (c == "x")
                    {
                        infijo[k] = c;
                        k++;
                    }
                    i = j;
                }//Paréntesis (
                else if (c == "(")
                {
                    p.Push(c);
                }//Paréntesis )
                else if (c == ")")
                {
                    while ((p.Peek().ToString() != "("))
                    {
                        infijo[k] = p.Pop().ToString();
                        k++;
                    }
                    p.Pop();
                }
                //Operandos 
                //Funciones seno, coseno, tangente, logaritmo, raiz cuadrada
                else if (c == "-" || c == "+" || c == "*" || c == "/" || c == "T" || c == "S" || c == "C" || c == "L" || c == "^" || c == "E")
                {
                    j = i;
                    tmp = "";
                    while (char.IsLetter(ecuacion, j))
                    {
                        tmp = tmp + ecuacion[j].ToString();
                        j++;
                        band3++;
                    }
                    if (band3 > 0)
                    {
                        p.Push(tmp);
                        j--;
                    }
                    i = j;
                    if (band3 == 0)
                    {
                        while ((p.Count > 0) && (p.Peek().ToString() != "(") && (prioridad(p.Peek().ToString()) >= prioridad(c)))
                        {
                            infijo[k] = p.Pop().ToString();
                            k++;
                            band3++;
                        }
                        p.Push(c);
                    }
                }
            }
            while (p.Count > 0)
            {
                infijo[k] = p.Pop().ToString();
                k++;
            }

            return infijo;
        }

        public double evaluacion(string[] val, double x)
        {
            int i = 0;
            string operando1; string operando2;
            double op1; double op2;

            string c;
            double res = 0;
            for (i = 0; i < val.Length; i++)
            {
                int j = 0;
                if (val[i] == null)
                    break;
                c = val[i].ToString();

                if (operador(c))
                {
                    if (c == "+" || c == "-" || c == "*" || c == "/" || c == "^")
                    {
                        operando2 = p.Pop().ToString();
                        operando1 = p.Pop().ToString();
                        if (operando2 == "x")
                        {
                            op2 = x;
                        }
                        else
                        {
                            op2 = Convert.ToDouble(operando2);
                        }
                        if (operando1 == "x")
                        {
                            op1 = x;
                        }
                        else
                        {
                            op1 = Convert.ToDouble(operando1);
                        }
                        switch (c)
                        {
                            case "+":
                                res = op1 + op2;
                                p.Push(res);
                                break;
                            case "-":
                                res = op1 - op2;
                                p.Push(res);
                                break;
                            case "*":
                                res = op1 * op2;
                                p.Push(res);
                                break;
                            case "/":
                                res = op1 / op2;
                                p.Push(res);
                                break;
                            case "^":
                                res = Math.Pow(op1, op2);
                                p.Push(res);
                                break;
                            default:
                                break;
                        }
                    }
                    else
                    {

                        operando1 = p.Pop().ToString();
                        if (operando1 == "x")
                        {
                            op1 = x;
                        }
                        else
                        {
                            op1 = Convert.ToDouble(operando1);
                        }
                        switch (c)
                        {

                            case "Tan":
                                res = Math.Tan(op1);
                                p.Push(res);
                                break;
                            case "Cos":
                                res = Math.Cos(op1);
                                p.Push(res);
                                break;
                            case "Sen":
                                res = Math.Sin(op1);
                                p.Push(res);
                                break;
                            case "Log":
                                res = Math.Log(op1);
                                p.Push(res);
                                break;
                            case "Sqrt":
                                res = Math.Sqrt(op1);
                                p.Push(res);
                                break;
                            case "Exp":
                                res = Math.Exp(op1);
                                p.Push(res);
                                break;
                            default:
                                break;
                        }
                    }
                }
                else
                {
                    p.Push(c);
                }
            }
            double eval = Convert.ToDouble(p.Pop().ToString());
            return eval;
        }

        private void button22_Click(object sender, EventArgs e)
        {
            if (clear > 0)
                txtEq.Text = "";
            txtEq.Text = txtEq.Text + "1"; clear = 0;
        }

        private void button2_Click(object sender, EventArgs e)
        {
            if (clear > 0)
                txtEq.Text = "";
            txtEq.Text = txtEq.Text + "2"; clear = 0;
        }

        private void button3_Click(object sender, EventArgs e)
        {
            if (clear > 0)
                txtEq.Text = "";
            txtEq.Text = txtEq.Text + "3"; clear = 0;
        }

        private void button6_Click(object sender, EventArgs e)
        {
            if (clear > 0)
                txtEq.Text = "";
            txtEq.Text = txtEq.Text + "4"; clear = 0;
        }

        private void button9_Click(object sender, EventArgs e)
        {
            if (clear > 0)
                txtEq.Text = "";
            txtEq.Text = txtEq.Text + "7"; clear = 0;
        }

        private void button5_Click(object sender, EventArgs e)
        {
            if (clear > 0)
                txtEq.Text = "";
            txtEq.Text = txtEq.Text + "5"; clear = 0;
        }

        private void button4_Click(object sender, EventArgs e)
        {
            if (clear > 0)
                txtEq.Text = "";
            txtEq.Text = txtEq.Text + "6"; clear = 0;
        }

        private void button8_Click(object sender, EventArgs e)
        {
            if (clear > 0)
                txtEq.Text = "";
            txtEq.Text = txtEq.Text + "8"; clear = 0;
        }

        private void button7_Click(object sender, EventArgs e)
        {
            if (clear > 0)
                txtEq.Text = "";
            txtEq.Text = txtEq.Text + "9"; clear = 0;
        }

        private void button10_Click(object sender, EventArgs e)
        {
            if (clear > 0)
                txtEq.Text = "";
            txtEq.Text = txtEq.Text + "0"; clear = 0;
        }

        private void button11_Click(object sender, EventArgs e)
        {
            if (clear > 0)
                txtEq.Text = "";
            txtEq.Text = txtEq.Text + "+"; clear = 0;
        }

        private void button20_Click(object sender, EventArgs e)
        {
            
            if (txtEq.Text == "")
            {
                MessageBox.Show("Expresión Vacía", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
            }
            else
            {
                try
                {
                   
                    txtEq.Text = txtEq.Text + "\n\n" + Convert.ToString(evaluacion(postfijo(txtEq.Text), 1));
                }
                catch (Exception ex)
                {
                    MessageBox.Show(ex.Message, "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
                }
            }
            clear++;
        }

        private void button12_Click(object sender, EventArgs e)
        {
            if (clear > 0)
                txtEq.Text = "";
            txtEq.Text = txtEq.Text + "-"; clear = 0;
        }

        private void button13_Click(object sender, EventArgs e)
        {
            if (clear > 0)
                txtEq.Text = "";
            txtEq.Text = txtEq.Text + "*"; clear = 0;
        }

        private void button21_Click(object sender, EventArgs e)
        {
            if (clear > 0)
                txtEq.Text = "";
            txtEq.Text = txtEq.Text + "^"; clear = 0;
        }

        private void button14_Click(object sender, EventArgs e)
        {
            if (clear > 0)
                txtEq.Text = "";
            txtEq.Text = txtEq.Text + "/"; clear = 0;
        }

        private void button38_Click(object sender, EventArgs e)
        {
            if (clear > 0)
                txtEq.Text = "";
            txtEq.Text = txtEq.Text + "."; clear = 0;
        }

        private void button39_Click(object sender, EventArgs e)
        {
            if (clear > 0)
                txtEq.Text = "";
            txtEq.Text = txtEq.Text + "Exp("; clear = 0;
        }

        private void button19_Click(object sender, EventArgs e)
        {
            if (clear > 0)
                txtEq.Text = "";
            txtEq.Text = txtEq.Text + "Sqrt("; clear = 0;
        }

        private void button27_Click(object sender, EventArgs e)
        {
            if (clear > 0)
                txtEq.Text = "";
            txtEq.Text = txtEq.Text + "("; clear = 0;
        }

        private void button28_Click(object sender, EventArgs e)
        {
            if (clear > 0)
                txtEq.Text = "";
            txtEq.Text = txtEq.Text + ")";
            clear = 0;
        }

        private void button18_Click(object sender, EventArgs e)
        {
            if (clear > 0)
                txtEq.Text = "";
            txtEq.Text = txtEq.Text + "Log("; clear = 0;
        }

        private void button16_Click(object sender, EventArgs e)
        {
            if (clear > 0)
                txtEq.Text = "";
            txtEq.Text = txtEq.Text + "Cos("; clear = 0;
        }

        private void button15_Click(object sender, EventArgs e)
        {
            if (clear > 0)
                txtEq.Text = "";
            txtEq.Text = txtEq.Text + "Sen("; clear = 0;
        }

        private void button17_Click(object sender, EventArgs e)
        {
            if (clear > 0)
                txtEq.Text = "";
            txtEq.Text = txtEq.Text + "Tan("; clear = 0;
        }

        private void button24_Click(object sender, EventArgs e)
        {
            txtEq.Text = "";
        }

        private void button23_Click(object sender, EventArgs e)
        {
            int i = txtEq.Text.Length;
            try
            {
                txtEq.Text = txtEq.Text.Remove(i - 1, 1);
            }
            catch (Exception ex)
            {
                MessageBox.Show("No hay nada para eliminar, error: " + ex.Message, "Error", MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
            }
        }

        private void txtEq_KeyPress(object sender, KeyPressEventArgs e)
        {

        }

        private void txtEq_KeyDown(object sender, KeyEventArgs e)
        {
            if (e.KeyValue < 47 || e.KeyValue > 58)
                e.SuppressKeyPress = true;
            else if (e.KeyData == Keys.Decimal || e.KeyData == Keys.Divide || e.KeyData == Keys.Subtract)
                e.SuppressKeyPress = false;
        }

        private void txtEq_Enter(object sender, EventArgs e)
        {
            
        }

        private void Calculadora_Load(object sender, EventArgs e)
        {

        }

        private void button26_Click(object sender, EventArgs e)
        {
            if (clear > 0)
            { 
              
            }
        }
    }
}