TRADE_ACTION_SLT error -> Invalid request

[Nuno Madeira Amaro Pire Costa]

My Trailing SL function no longer works. Maybe it is because of my NormalizeDouble routine.

Normalize Double:

//NormalizeDdouble(double,par);
double ND(double val, string par) {
//   return(NormalizeDouble(val,StringLen(SymbolInfoDouble(par,SYMBOL_POINT))));
   return(NormalizeDouble(val,SymbolInfoInteger(par,SYMBOL_DIGITS)));
}

Why I think this might be the issue:

halfway in my Trailing SL funcion I have this debug monitor:

if(par_temp==Symbol()) printf("ENTROU NA SL -> "+ND(New_TSL,par_temp);

Which returns:

2022.07.25 12:04:14.073 NMC_Proj (EURAUD,M15) ENTROU NA SL -> 1.4728000164031982

Where I expected it to say  ENTROU NA SL -> 1.47280

My Trailing stop is not being moved and I get the following error:

2022.07.25 12:05:29.553 Trades '5004787288': failed modify #0 buy 0  sl: 0.00000, tp: 0.00000 -> sl: 136.32700, tp: 136.80100 [Invalid request]

My TSL request was not changed and looks like this:

      MqlTradeRequest request= {};
      MqlTradeResult result= {};
      ZeroMemory(request);
      ZeroMemory(result);
      
      request.action  =TRADE_ACTION_SLTP; // type of trade operation
      request.position=ticket;   // ticket of the position
      request.symbol=par_temp; // symbol
      request.sl     =ND(New_TSL,par_temp);                // Stop Loss of the position
      request.tp     =PositionGetDouble(POSITION_TP);                // Take Profit of the position
      request.magic  =PositionGetInteger(POSITION_MAGIC);         // MagicNumber of the position
      if(request.sl>0) OrderSend(request,result);

I trying changing the ND funcion around, and I tried using the NormalizeDouble(New_TSL,5) and neither worked.

What else can I look at? I am picking up the position tickets correctly but somewhere along the way my double format doesn't get normalized.

[William Roeder]

You used NormalizeDouble, It's use is usually wrong, as it is in your case.

1. Floating point has a infinite number of decimals, it's your not understanding floating point and that some numbers can't be represented exactly. (like 1/10.)
             Double-precision floating-point format - Wikipedia, the free encyclopedia

   See also The == operand. - MQL4 programming forum (2013)

2. Print out your values to the precision you want with DoubleToString - Conversion Functions - MQL4 Reference.

3. SL/TP (stops) need to be normalized to tick size (not Point) — code fails on non-currencies.
             On 5Digit Broker Stops are only allowed to be placed on full pip values. How to find out in mql? - MQL4 programming forum (2011)

   And abide by the limits Requirements and Limitations in Making Trades - Appendixes - MQL4 Tutorial and that requires understanding floating point equality Can price != price ? - MQL4 programming forum (2012)

4. Open price for pending orders need to be adjusted. On Currencies, Point == TickSize, so you will get the same answer, but it won't work on non-currencies. So do it right.
             Trailing Bar Entry EA - MQL4 programming forum (2013)
             Bid/Ask: (No Need) to use NormalizeDouble in OrderSend - MQL4 programming forum (2012)

5. Lot size must also be adjusted to a multiple of LotStep and check against min and max. If that is not a power of 1/10 then NormalizeDouble is wrong. Do it right.
             (MT4 2013)) (MT5 2022))

6. MathRound() and NormalizeDouble() are rounding in a different way. Make it explicit.
             MT4:NormalizeDouble - MQL5 programming forum (2017)
             How to Normalize - Expert Advisors and Automated Trading - MQL5 programming forum (2017)

7. Prices you get from the terminal are already correct (normalized).

8. PIP, Point, or Tick are all different in general.
             What is a TICK? - MQL4 programming forum (2014)

[Nuno Madeira Amaro Pire Costa]

Thanks, this will give me plenty to work on.

Thanks for teaching us how to fish, it is way better than giving us free fish!

[Nuno Madeira Amaro Pire Costa]

It works after the following changes:

Normalize function:

//NormalizeDdouble(double,par);
double ND(double value, string par) {
   double TickSize=SymbolInfoDouble(par,SYMBOL_TRADE_TICK_SIZE);
   return(MathRound(value/TickSize)*TickSize);
}

on the Trailing function, replaced the request method from:

      MqlTradeRequest request= {};
      MqlTradeResult result= {};
      ZeroMemory(request);
      ZeroMemory(result);
      
      request.action  =TRADE_ACTION_SLTP; // type of trade operation
      request.position=ticket;   // ticket of the position
      request.symbol=par_temp; // symbol
      request.sl     =ND(New_TSL,par_temp);                // Stop Loss of the position
      request.tp     =PositionGetDouble(POSITION_TP);                // Take Profit of the position
      request.magic  =PositionGetInteger(POSITION_MAGIC);         // MagicNumber of the position
      if(request.sl>0) OrderSend(request,result); // Original SL moving method

to:

      m_trade.PositionModify(m_position.Ticket(), ND(New_TSL,par_temp), PositionGetDouble(POSITION_TP)); // New SL moving method

Thank you for your input, @William Roeder