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MQL equivalent to Python's None type? - page 9

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Форум по трейдингу, автоматическим торговым системам и тестированию торговых стратегий

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fxsaber, 2018.10.29 21:40

int Ref( string &Str ) { return(Str == NULL ? 1 : 0); }
int Val( string  Str ) { return(Str == NULL ? 1 : 0); }

#define ITERATIONS 1e5

int BenchRef( const string &Str, const int Iterations = ITERATIONS )
{
  int Res = 0;
  
  for (int i = 0; i < Iterations; i++)
  {
    string Str2 = (string)i + Str;
    
    Res += Ref(Str2);
  }
    
  return(Res);
}

int BenchVal( const string &Str, const int Iterations = ITERATIONS )
{
  int Res = 0;
  
  for (int i = 0; i < Iterations; i++)
    Res += Val((string)i + Str);
    
  return(Res);
}

#define _CS(A) ((!::IsStopped()) && (A))

#define BENCH(A,B)                                           \
{                                                            \
  ulong MinTime = ULONG_MAX;                                 \
  for (int i = 0; _CS(i < B); i++)                           \
  {                                                          \
    Comment(#A + ": " + (string)i + "/" + #B);               \
                                                             \
    const ulong StartTime=GetMicrosecondCount();             \
    A;                                                       \
    const ulong TmpTime = GetMicrosecondCount() - StartTime; \
                                                             \
    if (TmpTime < MinTime)                                   \
      MinTime = TmpTime;                                     \
  }                                                          \
                                                             \
  Print("Time["+#A+"] = "+(string)MinTime);                  \
}

void OnStart()
{
  string Str = " ";
  
  for (int i = 0; i < 16; i++)
    Str += Str;
    
  BENCH(BenchRef(Str), 100)
  BENCH(BenchVal(Str), 100)
}


Time[BenchRef(Str)] = 545708
Time[BenchVal(Str)] = 543934
Amir Yacoby:
That's correct.
Btw, there's another interesting use for this lib that crossed my mind. 
You can pass to functions/methods any combination of parameters with default values (not restricted to the end of parameters list)

*-in that case it is better to give the default positive value in the function method itself (for parm2=5.1):

Which allows to call without the caller knowing the actual default value of the 2nd parameter.


That made me think of another possible use... Set a variable to none by reference and also set an entire array to none. 

#ifdef __MQL4__
#property strict
#endif 

#define NONE_DOUBLE  DBL_MAX
#define NONE_FLOAT   FLT_MAX
#define NONE_INT     INT_MAX
#define NONE_UINT    UINT_MAX
#define NONE_LONG    LONG_MAX
#define NONE_ULONG   ULONG_MAX
#define NONE_CHAR    CHAR_MAX
#define NONE_UCHAR   UCHAR_MAX
#define NONE_SHORT   SHORT_MAX
#define NONE_USHORT  USHORT_MAX
#define NONE_COLOR   clrNONE
#define NONE_DATETIME -1
#define NONE_POINTER NULL
#define NONE_STRING  "__NONE-*-*-STRING__"

class _NoneType
{
 public:
   static double   None(double _)     { return NONE_DOUBLE;}
   static float    None(float _)      { return NONE_FLOAT; }
   static int      None(int _)        { return NONE_INT;   }
   static uint     None(uint _)       { return NONE_UINT;  }
   static long     None(long _)       { return NONE_LONG;  }
   static ulong    None(ulong _)      { return NONE_ULONG; }
   static char     None(char _)       { return NONE_CHAR;  }
   static uchar    None(uchar _)      { return NONE_UCHAR; }
   static short    None(short _)      { return NONE_SHORT; }
   static ushort   None(ushort _)     { return NONE_USHORT;}
   static string   None(string _)     { return NONE_STRING;}
   static color    None(color _)      { return NONE_COLOR; }
   static datetime None(datetime _)   { return NONE_DATETIME;}
   template<typename T>
   static T        None(T _)          { return NONE_POINTER;}
   
   static bool    IsNone( const double   Value ) { return(Value == NONE_DOUBLE); }
   static bool    IsNone( const float    Value ) { return(Value == NONE_FLOAT); }
   static bool    IsNone( const int      Value ) { return(Value == NONE_INT); }
   static bool    IsNone( const uint     Value ) { return(Value == NONE_UINT); }
   static bool    IsNone( const long     Value ) { return(Value == NONE_LONG); }
   static bool    IsNone( const ulong    Value ) { return(Value == NONE_ULONG); }
   static bool    IsNone( const char     Value ) { return(Value == NONE_CHAR); }
   static bool    IsNone( const uchar    Value ) { return(Value == NONE_UCHAR); }
   static bool    IsNone( const short    Value ) { return(Value == NONE_SHORT); }
   static bool    IsNone( const ushort   Value ) { return(Value == NONE_USHORT); }
   static bool    IsNone( const color    Value ) { return(Value == NONE_COLOR); }
   static bool    IsNone( const datetime Value ) { return(Value == NONE_DATETIME); }
   static bool    IsNone( const string   Value ) { return(Value == NONE_STRING); }
   template<typename T>
   static bool    IsNone( const T         Value ) { return(Value == NONE_POINTER);}
   
   static void    SetNone(double   &Value ) { Value = NONE_DOUBLE; }
   static void    SetNone(float    &Value ) { Value = NONE_FLOAT; }
   static void    SetNone(int      &Value ) { Value = NONE_INT; }
   static void    SetNone(uint     &Value ) { Value = NONE_UINT; }
   static void    SetNone(long     &Value ) { Value = NONE_LONG; }
   static void    SetNone(ulong    &Value ) { Value = NONE_ULONG; }
   static void    SetNone(char     &Value ) { Value = NONE_CHAR; }
   static void    SetNone(uchar    &Value ) { Value = NONE_UCHAR; }
   static void    SetNone(short    &Value ) { Value = NONE_SHORT; }
   static void    SetNone(ushort   &Value ) { Value = NONE_USHORT; }
   static void    SetNone(color    &Value ) { Value = NONE_COLOR; }
   static void    SetNone(datetime &Value ) { Value = NONE_DATETIME; }
   static void    SetNone(string   &Value ) { Value = NONE_STRING; }
   template<typename T>
   static void    SetNone(T        Value)  { 
      if(CheckPointer(Value) == POINTER_DYNAMIC){
         delete Value;
         Value = NONE_POINTER;
      }
   }  
   template <typename T>
   static void    ArraySetNone(T &array[]){
      for(int i=ArraySize(array)-1; i>=0; --i)
         SetNone(array[i]);
   }
};

#define NONE(T)                _NoneType::None((T)NULL)
#define IS_NONE(VALUE)         _NoneType::IsNone(VALUE)
#define SET_NONE(BY_REF)       _NoneType::SetNone(BY_REF)  
#define ARRAY_SET_NONE(ARRAY)  _NoneType::ArraySetNone(ARRAY)
  
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