The fastes shift all element on Array to left (shift one position inside array)

[[Deleted]]

Hi guys,

I have array, 100 elements and I need shift all elements left, index 99 bye bye :-) from index 98 to index 99, 97->98, 2->3 .... index 0 = zero

What is the fastes solution for it? Exist any special mql function?

Or basic solution ...:

int count=ArraySize(array);
for(int i=count-2; i>1; i--) array[i]=array[i-1];
array[0]=0;

[William Roeder]

From my code

bool     ResizeBuffer(double& buffer[], int size){ // buffer can be 1D or 2D
   if(ArrayRange(buffer,0) != size){      // ArrayRange allows 1D or 2D arrays
      ArraySetAsSeries(buffer, false);    // Shift values B[2]=B[1]; B[1]=B[0]
      if( !MyArrayResize(buffer, size, "ResizeBuffer") )        return(false);
      ArraySetAsSeries(buffer, true);
   }
   return(true);
}
bool     MyArrayResize(double& arr[], int nRows, string msg){
   if( ArrayResize(arr, nRows) >= nRows)  return(true);
   DisableTrading( "ArrayResize("+nRows+") Failed: "+GetLastError() +" "+msg);
   return(false);
}
////////////////
double Typical[]; datetime TypicalCounted=0;
int start(){
  ResizeBuffer(Typical, Bars); 
  for(int iBar=iBarShift(NULL,0,TypicalCounted); iBar >=0; iBar--) 
     Typical[iBar] = (High[iBar]+Low[iBar]+Close[iBar])/3;
  TypicalCounted = TimeCurrent();

  Print("3 bars ago typical price was "+PriceToStr(Typical[3]));

No shifting required.

[GreenMoney]

endy5:

I have array, 100 elements and I need shift all elements left, index 99 bye bye :-) from index 98 to index 99, 97->98, 2->3 .... index 0 = zero

What is the fastes solution for it? Exist any special mql function?

I don't know about the fastest, but you could simply use ArrayCopy() to shift the elements:

int count = ArraySize(array);
if (ArrayCopy(array, array, 1, 0, count - 1) == count - 1)
   array[0] = 0;

[Roel]

Old thread, I know, but this may help someone. It seems like the original code listed has "-2" and that should read "-1"  and it has ">1" which should read ">=1" - correct?

[James Kirika Wanjiru]

//+------------------------------------------------------------------+
//|                                                   arrayshift.mq5 |
//|                                  Copyright 2023, MetaQuotes Ltd. |
//|                                             https://www.mql5.com |
//+------------------------------------------------------------------+
#property copyright "Copyright 2023, MetaQuotes Ltd."
#property link      "https://www.mql5.com"
#property version   "1.00"   
//+------------------------------------------------------------------+
//| Script program start function                                    |
//+------------------------------------------------------------------+
void OnStart()
  {
//---    
    ulong array[]; 
    addelements(array);
    shiftleft(array);
   
  }
//+------------------------------------------------------------------+
void addelements(ulong &array[])  //Add 10 elements to a dynamic array
{  

  for(int i=0;i<10;i++)
  {
    ArrayResize(array,i+1,i+2);  
    array[i]=i;
  } 
   
}

void shiftleft(ulong &array[])   //remove first element then shift the whole array one step to the left
{
  for(int i=0;i<ArraySize(array);i++)
  Print(array[i]);  //This prints the 0123456789
  Print("Br");
  ArrayReverse(array,0,ArraySize(array));  //flip array
  for(int i=0;i<ArraySize(array);i++)
  Print(array[i]);  //This prints the 9876543210
  Print("Br");
  ArrayResize(array,ArraySize(array)-1,ArraySize(array)); //discard last elemet
  ArrayReverse(array,0,ArraySize(array));
  for(int i=0;i<ArraySize(array);i++)
  Print(array[i]);  //This prints the 123456789 note 1st element is gone
}

I know its an old thread but I had a task where I needed to shift all elements of array to the left, I came up with a simple code see the above script. NB, my code is open to critism alongside improvements feel free, after all we here to learn :-).

[Dominik Egert]

James Kirika Wanjiru #:

I know its an old thread but I had a task where I needed to shift all elements of array to the left, I came up with a simple code see the above script. NB, my code is open to critism alongside improvements feel free, after all we here to learn :-).

Your code copies the array twice, with two malloc calls.

This is in place and should be faster, but not tested for speed:

const int array_size = ArraySize(array);
for(int cnt = 1; cnt < array_size; cnt++)
{
  array[cnt - 1] = array[cnt];
}
ArrayResize(array, array_size - 1);

EDIT:

According to docs, this has undefined behavior:

ArrayCopy(array, array, 1, 0, count - 1);

[Carl Schreiber]

Instead of copying each element of an array just 'move' the index: see: https://www.mql5.com/en/articles/3047