// Calc.cs - 表达式计算器
// 编译方法: csc /t:winexe Calc.cs VBExpression.cs

using System;
using System.Windows.Forms;
using Skyiv.Util;

namespace Skyiv
{
  class Calc : Form
  {
    TextBox tbxA1, tbxA2, tbxA3;

    Calc()
    {
      Text              = "表达式计算器";
      StartPosition     = FormStartPosition.CenterScreen;
      Width             = 400;
      Height            = 200;

      Label lblA1       = new Label();
      lblA1.Text        = "表达式(&E)";
      lblA1.Parent      = this;
      lblA1.Top         = 23;
      lblA1.Left        = 10;
      lblA1.AutoSize    = true;

      tbxA1             = new TextBox();
      tbxA1.Parent      = this;
      tbxA1.Top         = 20;
      tbxA1.Left        = 80;
      tbxA1.Width       = 300;
      tbxA1.BorderStyle = BorderStyle.FixedSingle;

      Label lblA2       = new Label();
      lblA2.Text        = "自变量(&X)";
      lblA2.Parent      = this;
      lblA2.Top         = 48;
      lblA2.Left        = 10;
      lblA2.AutoSize    = true;

      tbxA2             = new TextBox();
      tbxA2.Parent      = this;
      tbxA2.Top         = 45;
      tbxA2.Left        = 80;
      tbxA2.Width       = 300;
      tbxA2.BorderStyle = BorderStyle.FixedSingle;

      Button btnA3      = new Button();
      btnA3.Text        = "计算(&C)";
      btnA3.Parent      = this;
      btnA3.Top         = 70;
      btnA3.Left        = 10;
      btnA3.Width       = 62;
      btnA3.Click      += new EventHandler(Calc_Clicked);

      tbxA3             = new TextBox();
      tbxA3.Parent      = this;
      tbxA3.Top         = 70;
      tbxA3.Left        = 80;
      tbxA3.Width       = 300;
      tbxA3.BorderStyle = BorderStyle.FixedSingle;
      tbxA3.ReadOnly    = true;


      TextBox tbxA4     = new TextBox();
      tbxA4.Text        = @"
表达式使用 Visual Baisc 语法，可带一个的自变量(x)
可使用 pi、e 等常量，sin、cos、tan、log、sqrt 等函数
例子：x * cos(x * pi / sqrt(25 * 6^4)) + log(E^10)";
      tbxA4.Parent      = this;
      tbxA4.Top         = 95;
      tbxA4.Left        = 10;
      tbxA4.Width       = 370;
      tbxA4.Height      = 65;
      tbxA4.BorderStyle = BorderStyle.None;
      tbxA4.Multiline   = true;
      tbxA4.ReadOnly    = true;
    }

    void Calc_Clicked(object sender, EventArgs ea)
    {
      (sender as Control).Enabled = false;
      try
      {
        double x = 0;
        if (tbxA2.Text.Trim().Length != 0)
        {
          try
          {
            x = double.Parse(tbxA2.Text);
          }
          catch
          {
            try