double fst;
        double snd;
        double exp;
        Char action;
        Calc solver;
        bool pnt;
        bool neg;
        public CalcForm()
        {
            InitializeComponent();
            pnt = false;
            neg = false;
            action = '@';
            solver = new Calc();
        }

        private void button_0_Click(object sender, EventArgs e)
        {
            exprEdit.Text = exprEdit.Text + "0";
        }

        private void button_1_Click(object sender, EventArgs e)
        {
            exprEdit.Text = exprEdit.Text + "1";
        }

        private void button_point_Click(object sender, EventArgs e)
        {
            if (!pnt)
            {
                exprEdit.Text = exprEdit.Text + ",";
                pnt = true;
            }
            else MessageBox.Show("Point is already placed", "Input error", MessageBoxButtons.OK, MessageBoxIcon.Error);
        }

        private void button_2_Click(object sender, EventArgs e)
        {
            exprEdit.Text = exprEdit.Text + "2";
        }

        private void button_3_Click(object sender, EventArgs e)
        {
            exprEdit.Text = exprEdit.Text + "3";
        }

        private void button_4_Click(object sender, EventArgs e)
        {
            exprEdit.Text = exprEdit.Text + "4";
        }

        private void button_5_Click(object sender, EventArgs e)
        {
            exprEdit.Text = exprEdit.Text + "5";
        }

        private void button_6_Click(object sender, EventArgs e)
        {
            exprEdit.Text = exprEdit.Text + "6";
        }

        private void button_7_Click(object sender, EventArgs e)
        {
            exprEdit.Text = exprEdit.Text + "7";
        }

        private void button_8_Click(object sender, EventArgs e)
        {
            exprEdit.Text = exprEdit.Text + "8";
        }

        private void button_9_Click(object sender, EventArgs e)
        {
            exprEdit.Text = exprEdit.Text + "9";
        }

        private void button_summ_Click(object sender, EventArgs e)
        {
            if(!action.Equals('@'))
            {
                String[] tokens = exprEdit.Text.Split(action);
                if(!double.TryParse(tokens[tokens.Length - 1], out snd))
                {
                    MessageBox.Show("Second number is not inputed", "Input error", MessageBoxButtons.OK, MessageBoxIcon.Error);
                    return;
                }
                if (neg) snd *= -1;
                fst = compute();
                exprEdit.Text = System.Convert.ToString(fst);
            }

            if(exprEdit.Text.Equals(""))
                MessageBox.Show("First number is not inputed", "Input error", MessageBoxButtons.OK, MessageBoxIcon.Error);
            else
            {
                double.TryParse(exprEdit.Text, out fst);
                if (neg) fst *= -1;
                exprEdit.Text = exprEdit.Text + " + ";
                action = '+';
                pnt = false;
                neg = false;
            }
        }

        private void button_sub_Click(object sender, EventArgs e)
        {
            if (!action.Equals('@'))
            {
                String[] tokens = exprEdit.Text.Split(action);
                if (!double.TryParse(tokens[tokens.Length - 1], out snd))
                {
                    MessageBox.Show("Second number is not inputed", "Input error", MessageBoxButtons.OK, MessageBoxIcon.Error);
                    return;
                }
                if (neg) snd *= -1;
                fst = compute();
                exprEdit.Text = System.Convert.ToString(fst);
            }

            if (exprEdit.Text.Equals(""))
                MessageBox.Show("First number is not inputed", "Input error", MessageBoxButtons.OK, MessageBoxIcon.Error);
            else
            {
                double.TryParse(exprEdit.Text, out fst);
                exprEdit.Text = exprEdit.Text + " - ";
                action = '-';
                pnt = false;
                neg = false;
            }
        }

        private void button_mult_Click(object sender, EventArgs e)
        {
            if (!action.Equals('@'))
            {
                String[] tokens = exprEdit.Text.Split(action);
                if (!double.TryParse(tokens[tokens.Length - 1], out snd))
                {
                    MessageBox.Show("Second number is not inputed", "Input error", MessageBoxButtons.OK, MessageBoxIcon.Error);
                    return;
                }
                if (neg) snd *= -1;
                fst = compute();
                exprEdit.Text = System.Convert.ToString(fst);
            }

            if (exprEdit.Text.Equals(""))
                MessageBox.Show("First number is not inputed", "Input error", MessageBoxButtons.OK, MessageBoxIcon.Error);
            else
            {
                double.TryParse(exprEdit.Text, out fst);
                exprEdit.Text = exprEdit.Text + " * ";
                action = '*';
                pnt = false;
                neg = false;
            }
        }

        private void button_div_Click(object sender, EventArgs e)
        {
            if (!action.Equals('@'))
            {
                String[] tokens = exprEdit.Text.Split(action);
                if (!double.TryParse(tokens[tokens.Length - 1], out snd))
                {
                    MessageBox.Show("Second number is not inputed", "Input error", MessageBoxButtons.OK, MessageBoxIcon.Error);
                    return;
                }
                if (neg) snd *= -1;
                fst = compute();
                exprEdit.Text = System.Convert.ToString(fst);
            }

            if (exprEdit.Text.Equals(""))
                MessageBox.Show("First number is not inputed", "Input error", MessageBoxButtons.OK, MessageBoxIcon.Error);
            else
            {
                double.TryParse(exprEdit.Text, out fst);
                exprEdit.Text = exprEdit.Text + " / ";
                action = '/';
                pnt = false;
                neg = false;
            }
        }

        private void button_compute_Click(object sender, EventArgs e)
        {
            if(action.Equals('@'))
            {
                MessageBox.Show("No operations to compute", "Input error", MessageBoxButtons.OK, MessageBoxIcon.Error);
                return;
            }

            String[] tokens = exprEdit.Text.Split(action);
            double.TryParse(tokens[tokens.Length-1], out snd);
            fst = compute();
            exprEdit.Text = System.Convert.ToString(fst);
            neg = false;
            pnt = false;
            action = '@';
        }

        double compute()
        {
            switch(action)
            {
                case '+': return solver.Summ(fst, snd);
                case '-': return solver.Substract(fst, snd);
                case '/': return solver.divide(fst, snd);
                case '*': return solver.Multiple(fst, snd);
                case '^': return solver.pow(fst, snd);
                default: return double.NaN;
            }
        }

        private void button_negate_Click(object sender, EventArgs e)
        {
            if (!neg)
            {
                if(action.Equals('@') && !exprEdit.Text.Equals(""))
                {
                    MessageBox.Show("Can't negate half of number", "Input error", MessageBoxButtons.OK, MessageBoxIcon.Error);
                    return;
                }

                String[] tokens = exprEdit.Text.Split(action);
                if (double.TryParse(tokens[tokens.Length - 1], out snd))
                {
                    MessageBox.Show("Can't negate half of number", "Input error", MessageBoxButtons.OK, MessageBoxIcon.Error);
                    return;
                }

                exprEdit.Text = exprEdit.Text + "-";
                neg = true;
            }
            else
            {
                MessageBox.Show("Number is already negated", "Input error", MessageBoxButtons.OK, MessageBoxIcon.Error);
                return;
            }
        }

        private void button_pow_Click(object sender, EventArgs e)
        {
            if (!action.Equals('@'))
            {
                String[] tokens = exprEdit.Text.Split(action);
                if (!double.TryParse(tokens[tokens.Length - 1], out snd))
                {
                    MessageBox.Show("Second number is not inputed", "Input error", MessageBoxButtons.OK, MessageBoxIcon.Error);
                    return;
                }
                if (neg) snd *= -1;
                fst = compute();
                exprEdit.Text = System.Convert.ToString(fst);
            }

            if (exprEdit.Text.Equals(""))
                MessageBox.Show("First number is not inputed", "Input error", MessageBoxButtons.OK, MessageBoxIcon.Error);
            else
            {
                double.TryParse(exprEdit.Text, out fst);
                exprEdit.Text = exprEdit.Text + "^";
                action = '^';
                pnt = false;
                neg = false;
            }
        }

        private void button_clear_Click(object sender, EventArgs e)
        {
            pnt = false;
            neg = false;
            action = '@';
            exprEdit.Text = "";
        }