Reversed array with MQL4

Question

With MetaTrader Terminal ( MQL4 ), I try to have a reversed array, that I append ( prepend ) items to.

So, on every tick, myArray[0] becomes the 'newest' value, and the previous value shifts to myArray[1] and so on.

But its harder then it sounds.

I tried like this ->

       double myArray        = [];                        // GLOBAL Dynamic array
extern int    maxArrayLength = 50;                        // EXTERN iterable

// -----------------------------------------------------------------------
bool   prependToReversedDoubleArray( double& theArray[], double value, int maxLength ) {

       int size = ArraySize( theArray );                 // LOCAL size
       ArraySetAsSeries(     theArray, false );          // Normalize the array ( left to right )
       ArrayResize(          theArray, size + 1 );       // Extend array length

       Alert( "test = ", size );

       theArray[size] = value;                           // Insert the new value
       ArraySetAsSeries(     theArray, true );           // Reverse the array again
       if ( ArraySize(       theArray ) > maxLength ) {
            ArrayResize(     theArray,    maxLength );
       }
       return( true );
}

prependToReversedDoubleArray( myArray, 0.1234, maxArrayLength );

Answer 1

thanks for all the good intel! I learned a lot from the explanations :)

The problem I had was, how to append values to the 'beginning' of a reversed array ( write to array[0] and shift the rest up ).

It still not non-blocking and probably not the fastest way, but it works for now.

Here is the solution, it also takes a 'maxLength' value, that keeps the array size as desired :) :

int prependToReversedDoubleArray(  double &theArray[],
                                   double  value,
                                   int     maxLength
                                   )
{   int newSize = ArraySize( theArray ) + 1;
    ArraySetAsSeries( theArray, false );     // Normalize the array (left to right)
    ArrayResize(      theArray, newSize );   // Extend array length

    theArray[newSize-1] = value;             // Insert the new value

    ArraySetAsSeries( theArray, true );      // Reverse the array again

    if (  maxLength > 0
       && newSize   > maxLength )            // Check if the max length is reached
    {     newSize   = maxLength;
          ArrayResize( theArray, maxLength );
    }
    return( newSize );
}