如何將C  程式轉為Pascal語法:(上集)
原文出處: by Paul Fulford of Komodo Software
翻譯:http://delphi.ktop.com.tw    將C   轉為 Pascal/Delphi
==============================
目錄
part I(上集)
        概論
        資料型態
        關鍵字
        敘述結尾
        變數宣告
        字串
        陣列
        數值的指定與比較
        常數宣告
        函數與程序
        with ... do敘述
        註解
        流程控制
part II(下集)
        物件導向結構
        Containers
        例外處理
        資料流(Streaming)
        專案檔的設計
        如何轉換
        結論    =================================
概論:
        這篇文章的目的是讓您了解C  與Object Pascal的不同
        也讓您能夠有能力將C  轉為Object Pascal(以下稱為OP)    =================================
資料型態            這一章可學到如何將 C   的資料型態 轉成 OP 的資料型態.
變數宣告時可參考下列對照表            C                OP         大小 (bytes)   值範圍
        ================ ========== ============== ==========================
        char             ----       1              -128 to 127
        ----             char       1              1 ASCII character
        int              integer    2              -32,768 to 32,767
        short            ----       2              -32,768 to 32,767
        ----             shortint   1              -128 to 127
        long             longint    4              -2,147,483,647 to 2,147,483,647
        unsigned char    byte       1              0 to 255
        unsigned int     word       2              0 to 65,535
        unsigned short   word       2              0 to 65,535
        unsigned long    ----       4              0 to 4,294,967,295
        
        float            single     4              3.4E-38 TO 3.4E 38
        double           double     8              1.7E-308 TO 1.7E 308
        long double      extended   10             3.4E-4932 TO 3.4E 4932
        ----             comp       8              1.7E-308 TO 1.7E 308
        ----             real (for backwards compatibility only -- use double)
        
        void             pointer    8              n/a -- an untyped pointer
        ----             boolean    1              True or False
        (C   may soon have a boolean type)
        String           ----       a C   standard object
        ----             string     an array of up to 255 ASCII characters
        ----             PChar      pointer to a null-terminated string
        ================ ========== ============== ==========================
        
=================================
關鍵字            C   有 59 個關鍵字, OP 有 60 個關鍵字. This does not include the many vendor
        C   大小寫有分 OP 大小寫不分
        
        C  的關鍵字
        asm  auto  break  case  catch  cdecl  char  class  const  const_cast  continue
        default  delete  do  double  dynamic_cast  else  enum  extern  far  float  for
        friend  goto  huge  if  inline  interrupt  int  near  new  operator  pascal  private
        protected  public  register  reinterpret_cast  return  short  signed  sizeof
        static  static_cast  struct  switch  template  this  throw  try  typedef  typeid
        union  unsigned  virtual  void  volatile  wchar_t  while            OP的關鍵字
        and  as  asm  array  begin  case  class  const  constructor  destructor  div  do        
        downto  else  end  except  exports  file  finally  for  function  goto  if  implementation      
        in  inherited  inline  initialization  interface  is  label  library  mod  nil  not     
        object  of  or  packed  procedure  program  property  raise  record  repeat  set  shl
        shr  string  then  to  try  type  unit  until  uses  var  while  with  xor    =================================
敘述結尾            C  敘述結尾
        大部份的敘述都用 ; 號結尾
        有一些例外如:
        #include 
        #define MAXNAMELENGTH 35
        
        OP敘述結尾
        所有的敘述都用 ; 號結尾    =================================
變數宣告            C  變數宣告
        變數名稱只有前32個字有效
        變數名稱宣告可在程式的任何地方宣告(當然,宣告後才可用)
        // ... 如在程式中宣告
        {
           char i;
           for (i=0;i<10;i  )
           {
              char sName[10]; // 在區塊中也可宣告變數
              int iCount, iLoop, iValToReach;
              double dMaxLoan, dTotal;
              float fMaxRate = 123.875;
           }
        }
        OP變數宣告
        變數名稱只有前63個字有效
        變數名稱要宣告在var之後,且要在function或procedure開始時宣告
        不可在區塊內宣告變數
        如:
        function PayBack_d(var dAmount: double): double;
        var
                iCount, iLoop, iValToReach: integer;
                dMaxLoan, dTotal, dMaxRate: double;
        begin
                dMaxRate := 123.875;
                {...}
                    =================================
字串            C  字串
        在C  現在也有了字串物件,但並不和以"\0"結束的char相容.
        大部份的字串就是char陣列,可以無限長度.
        下面是一些char陣列宣告的例子:
        char sName[26]; // 25 個chars長
        char psDemo[] = "Hello, there!"; 
        char * psDemo = new char[26];
        對字串變數最常做的事就是strcpy與strcat
        您要確定strcat或strcpy後的長度夠不夠存放.
        以下是strcpy/strcat的例子.
        class Ticker
        {
        ...
        public:
                char sBuf[10],
                     sLatestTrade[TRADELENGTHBUF],
                     saTradeRecords[50] [TRADELENGTHBUF];
                ...
                void OptnFormat2_v(unsigned long & ulQuantity,
                                   CompanyC * poC,
                                   int & iSeries);
                ...
        };
        ...
        void TickerC::OptnFormat2_v(unsigned long & ulQuantity,
                                    CompanyC * poC,
                                    int & iSeries)
        {
                ultoa(ulQuantity, sBuf, 10);
                strcpy(sLatestTrade, sBuf);
                AddMosToString_v(sLatestTrade,
                                                  poC->oSOS.oSeries[iSeries].oExpDate.enMonth);
                itoa(poC->oSOS.oSeries[iSeries].oExpDate.iDay, sBuf, 10);
                strcat(sLatestTrade, sBuf);
                strcat(sLatestTrade, poC->oS.sTicker);
                double dStrike = poC->oSOS.oSeries[iSeries].dStrike;
                gcvt(dStrike, 3, sBuf);
                strcat(sLatestTrade, sBuf);
                if(poC->oSOS.oSeries[iSeries].enCallPut == Call)
                        strcat(sLatestTrade, "Calls");
                else strcat(sLatestTrade, "Puts");
        }
        
        OP字串
        Delphi 1.0字串最多255bytes,Delphi 2.0以後無此限.
        在OP內的String所佔的記憶空間會比您宣告的大小大.
        因為字串為陣列,在陣列[0]放長度.
        例:
        var
                sMyName: string[25]; {最大25字元}
                sYourName: string;
        begin
                sMyName := 'Paul Fulford'; {單引號表字串}            在OP中,您可用:=和 處理字串運算,例:
        TickerC = class
                ...
                public
                sLatestTrade: string[TRADELENGTHBUF];
                saTradeRecords: TStringList;
                ...
                procedure TickerC.OptnFormat2(var lQuantity: longint;
                                             poC: CompanyC;
                                             var iSeries: integer);
                ...
        end;
        ...
        procedure TickerC.OptnFormat2(var lQuantity: longint;
                                          poC: CompanyC;
                                          var iSeries: integer);
        begin
                sLatestTrade := IntToStr(lQuantity);
                AddMosToString(sLatestTrade,
                                   poC.oSOS.oSeries[iSeries].oExpDate.enMonth);
                sLatestTrade := sLatestTrade  
                                IntToStr(poC.oSOS.oSeries[iSeries].oExpDate.iDay)  
                                poC.oS.sTicker  
                                FloatToStr(poC.oSOS.oSeries[iSeries].dStrike);
                if poC.oSOS.oSeries[iSeries].enCallPut = Call then
                        sLatestTrade := sLatestTrade   'Calls'
                else sLatestTrade := sLatestTrade   'Puts';
        end; {OptnFormat2}
        
        您會發現OP處理字串容易得多.
        C  中字串以"\0"結尾,OP中陣列[0]放字串長度.    =================================
陣列            陣列是資料的一序列排列.
        C  與OP的陣列宣告很不同.
        但取用方式很像.
        
        C  陣列
        陣列從0開始,第一個元素為 [0], 第二個為[1]...類推,初學者要小心
        // 宣告 陣列...
        DateC aoCANHolidays[SIZE_HOLIDAYARRAY];
        double dAverageLast31Days[31];
        // 取用陣列
        for(int i = 30, j = 29; i > 0; i--,j--)
                dAverageLast31Days[i] = dAverageLast31Days[j];
        
        OP陣列
        陣列通常從[1]開始,但也不全然.
        在Delphi中您也可以發現某些物件也是從[0]開始的.
        像TList就是從TList[0]開始,我們要小心看物件的說明文件.
        例子:
        var
                aoCANHolidays: array[1..SIZE_HOLIDAYARRAY] of DateC;
                dAverageLast31Days: array[1..31] of double;
                i,j: integer;
        begin
                j := 30;
                for i := 31 downto 2 do
                begin
                        dAverageLast31Days[i] = dAverageLast31Days[j];
                        Dec(j); { or j := j-1; }
                end;
                
                
        兩個語言都可用多維陣列,見下例:
        
        C  
                 double dMatrix[50] [20];
        
        OP
        var
                dMatrix: array[1..50, 1..20] of double;
        
        
=================================
數值的指定與比較            C  數值的指定與比較
        比較相等時用 == 號
        給定值時用 = 號
        如:
        if (dMaxRate == 15.75)
        { ...
                dMaxRate = 12.5;
        ...
        }
        
        OP數值的指定與比較
        比較相等時用 = 號
        給定值時用 := 號
        如:
        if dMaxRate = 15.75 then
        begin
        ...
                dMaxRate := 12.5;
        ...
        end;            有一個例外就是OP在Const的值的給定是用=號,如:
        const max=100;    =================================
常數宣告            常數是無法改變值的,所以一定要在宣告時給值.            C  常數宣告
        const int iMax = 2000;
        const double dMaxValue = 1234.75;
        也可用巨集定義常數
        #define nMAXAMOUNT 1000
        
        OP常數宣告
        function PayBack_d(var dAmount: double): double;
        const
                iMAX = 2000; {notice value assigned with single equal sign this time}
                dMAXVALUE = 1234.75;
        var
                iCount, iLoop, iValToReach: integer;
                dMaxLoan, dTotal, dMaxRate: double;
        begin
                dMaxRate := dMAXVALUE;
                {...}    =================================
函數與程序
        在C  中所有的Function一定會傳回值.
        在OP中function要傳回值,procedure不用
        在C  中所有的function一定要()號,就算無參數
        在OP中function無參數不用()號            C  函數與程序
        例:
        double IntSinceLastAddDate_d(double &dAvailCash); // prototype
        void SetNewIntRate(); // no parameters or return value
        ...
        double LoanC::IntSinceLastAddDate_d(double &dAvailCash)
        {
                double dSomething;
                ...
                return dSomething;
        }
        
        void LoanC::SetNewIntRate()
        { ... }
        
        
        OP函數與程序
        例:
        function IntSinceLastAddDate_d(var dAvailCash: double): double;
        procedure SetNewIntRate; {無參數也無傳回值}
        ...
        function LoanC.IntSinceLastAddDate_d(var dAvailCash: double): double;
        var
                dSomething: double;
        begin
                ...
                result := dSomething; 
                {the global variable "result" is assigned the return value!}
        end;
        
        procedure LoanC.SetNewIntRate;
        begin
        ...
        end;
        
        兩個語言可以在參數傳遞時採用 pass by valye 或 pass by reference:
        
        C   pass by value ... double IntSinceLastAddDate_d(double dAvailCash);
        OP pass by value ... function IntSinceLastAddDate_d(dAvailCash: double): double;            C   pass by reference ... double IntSinceLastAddDate_d(double &dAvailCash);
        OP pass by reference ... function IntSinceLastAddDate_d(var dAvailCash: double): double;            C   pass constant ... double IntSinceLastAddDate_d(const double dAvailCash);
        OP pass constant ... function IntSinceLastAddDate_d(const dAvailCash: double): double;    =================================
with ... do敘述            C  無 with .. DO敘述            在C  中當您要取用資料時:
                poC.oStock.aoTradesLast130Days[0].lVol = 0;
                poC.oStock.aoTradesLast130Days[0].dHigh = 0;
                poC.oStock.aoTradesLast130Days[0].dLow = 0;
                poC.oStock.aoTradesLast130Days[0].dClose = 0;            但在OP中可以簡化成:
                with poC.oStock.aoTradesLast130Days[0] do
                begin
                        lVol := 0;
                        dHigh := 0;
                        dLow := 0;
                        dClose := 0;
                end;
        
=================================
註解            C  
        有兩種
        // 雙斜線後為註解
        /*  註解  */
        
        OP
        有三種
        // 雙斜線後為註解
        { 註解 }
        (* 註解 *)    =================================
流程控制            有五種流程控制指令,C  與OP都有,用法滿像的.    ~~~~~~~~~~~~~~~~~~~~~~~~~
1) if ... else 指令
        
        C  
        
        if(<邏輯運算式>) // 一定要有()號
        { ...
        }
        else if(<邏輯運算式>)
        {...
        }
        else
        {...
        }
        
        OP
        
        if <邏輯運算式> then  // 不一定要有()號,因有then
        begin
        ...
        end
        else if <邏輯運算式> then
        begin
        ....
        end
        else
        begin
        ...
        end; {最後一個end才要加;分號}
            ~~~~~~~~~~~~~~~~~~~~~~~~~
2) switch/case ... 指令            C  
        
        switch()
        {
                case iX: ... break;
                case iY: ... break;
                default: ...
        }
        
        OP
        
        case  of
                {no "begin" here}
                iX: 
                begin
                ...
                end; {每個end都要;分號}
                iY:
                begin
                ...
                end;
                else {此處不用;號}
                begin
                ...
                end;
        end; {這個end要;分號}
        
        
~~~~~~~~~~~~~~~~~~~~~~~~~
3) for ... loop 指令            C  
        
        for(iCount = 0; iCount <= 10; iCount  )
        { 
                //  iCount  , 每次迴圈值加一
        ...
                break; // 中斷迴圈
                continue; // 跳到下一個迴圈
        ...
        }
        
        
        OP
        
        for iCount := 1 to 10 do
        begin
        ... {iCount每次自動加 1}
                break; { 中斷迴圈 }
                continue; { 跳至下一個迴圈 }
        ...
        end;
            ~~~~~~~~~~~~~~~~~~~~~~~~~
4) while ... loop 指令            C  
        
        while(<邏輯運算式>)
        {
        ...
                break; // 中斷迴圈
                continue; // 跳到下一個迴圈
        ...
        }
        
        
        OP
        
        while <邏輯運算式> do
        begin
        ...
                break; { 中斷迴圈 }
                continue; { 跳至下一個迴圈 }
        ...
        end;    ~~~~~~~~~~~~~~~~~~~~~~~~~
5) do/repeat ... 指令            C  
        
        do
        {
                // 邏輯運算式 False迴圈終止
        ...
                break; // 中斷迴圈
                continue; // 跳到下一個迴圈
        ...
        }while(<邏輯運算式>);
        
        
        OP
        
        repeat
                // 邏輯運算式 True迴圈終止
        ...
                break; { 中斷迴圈 }
                continue; { 跳至下一個迴圈 }
        ...
        until <邏輯運算式>;    =================================
(上集)...待續...