执行数学公式的函数 回复 "heyongan" 的问题

问题来源: http://www.cnblogs.com/del/archive/2008/08/16/1268786.html#1289015

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本例在 Delphi 2007 和 Delphi 2009 中均调试通过, 运行效果图:

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代码文件:

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unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls;

type
  TForm1 = class(TForm)
    Button1: TButton;
    Button2: TButton;
    Button3: TButton;
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
    procedure Button3Click(Sender: TObject);
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

uses ComObj;

//执行数学公式的函数 RunForm:
//原理是借用 JavaScrip 脚本, 代码参考的是 Delphi 的 Format 函数;
//第一个参数是公式, 公式中的常量要用 A B C D E F G H I J 十个大写字母依次标识;
//第二个参数是参数组, 按顺序给出常量值(使用字符串的方式);
//目前支持的函数在下面列着呢, 不过在这里为了和后面的参数区别只能都弄成小写.
function RunForm(Formula: string; const Args: array of const): string;
const
  f = 'acos    = Math.acos;' +
      'asin    = Math.asin;' +
      'atan    = Math.atan;' +
      'atan2   = Math.atan2;' +
      'ceil    = Math.ceil;' +
      'cos     = Math.cos;' +
      'e       = Math.E;' +
      'exp     = Math.exp;' +
      'floor   = Math.floor;' +
      'ln10    = Math.LN10;' +
      'ln2     = Math.LN2;' +
      'log     = Math.log;' +
      'log10e  = Math.LOG10E;' +
      'log2e   = Math.LOG2E;' +
      'max     = Math.max;' +
      'min     = Math.min;' +
      'pi      = Math.PI;' +
      'pow     = Math.pow;' +
      'random  = Math.random;' +
      'round   = Math.round;' +
      'sin     = Math.sin;' +
      'sqrt    = Math.sqrt;' +
      'sqrt2   = Math.SQRT2;' +
      'tan     = Math.tan;';
var
  Len, BufLen: Integer;
  Buffer: array[0..4095] of Char;
  script: OleVariant;
  i: Integer;
begin
  for i := 0 to 9 do
    Formula := StringReplace(Formula, Char(i+65), '%' + IntToStr(i) + ':s', [rfReplaceAll]);

  BufLen := Length(Buffer);
  if Length(Formula) < (Length(Buffer) - (Length(Buffer) div 4)) then
    Len := FormatBuf(Buffer, Length(Buffer) - 1, Pointer(Formula)^, Length(Formula), Args)
  else
  begin
    BufLen := Length(Formula);
    Len := BufLen;
  end;
  if Len >= BufLen - 1 then
  begin
    while Len >= BufLen - 1 do
    begin
      Inc(BufLen, BufLen);
      Result := '';
      SetLength(Result, BufLen);
{$IFDEF UNICODE}
      Len := FormatBuf(PChar(Result), BufLen - 1, Pointer(Formula)^, Length(Formula), Args);
{$ELSE}
      Len := FormatBuf(Pointer(Result)^, BufLen - 1, Pointer(Formula)^, Length(Formula), Args);
{$ENDIF}
    end;
    SetLength(Result, Len);
  end
  else
    SetString(Result, Buffer, Len);

  try
    script := CreateOleObject('ScriptControl');
    script.Language := 'JavaScript';
    script.ExecuteStatement(f + 'str = ' + Result);
    Result := script.Eval('str');
  except
    Result := 'Err';
  end;
end; {RunForm 函数结束}


//测试一: 注意第二个参数要以字符串数组的方式给出
procedure TForm1.Button1Click(Sender: TObject);
var
  s: string;
begin
  s := RunForm('(A + B) / (A - B)', ['6','4']); {这里 A = 6; B = 4}
//  s := RunForm('(6 + 4) / (6 - 4)', []);        {这样也可以}
  ShowMessage(s); {5}
end;

//测试二: 使用的命令有大小写的区别
procedure TForm1.Button2Click(Sender: TObject);
var
  s: string;
begin
  s := RunForm('sin(A) + cos(B) + tan(A)', ['0.8','0.9']);
  ShowMessage(s); {2.36860461622055}
end;

//测试三, 可以使用 JavaScript 的常量, 不过要用小写字母
procedure TForm1.Button3Click(Sender: TObject);
var
  s: string;
begin
  s := RunForm('sqrt(pow(A, 2))', ['pi']);
  ShowMessage(s); {3.14159265358979}
end;

end.

窗体文件:

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object Form1: TForm1
  Left = 0
  Top = 0
  Caption = 'Form1'
  ClientHeight = 130
  ClientWidth = 206
  Color = clBtnFace
  Font.Charset = DEFAULT_CHARSET
  Font.Color = clWindowText
  Font.Height = -11
  Font.Name = 'Tahoma'
  Font.Style = []
  OldCreateOrder = False
  Position = poDesktopCenter
  PixelsPerInch = 96
  TextHeight = 13
  object Button1: TButton
    Left = 64
    Top = 24
    Width = 75
    Height = 25
    Caption = 'Button1'
    TabOrder = 0
    OnClick = Button1Click
  end
  object Button2: TButton
    Left = 64
    Top = 55
    Width = 75
    Height = 25
    Caption = 'Button2'
    TabOrder = 1
    OnClick = Button2Click
  end
  object Button3: TButton
    Left = 64
    Top = 86
    Width = 75
    Height = 25
    Caption = 'Button3'
    TabOrder = 2
    OnClick = Button3Click
  end
end