The following code was extracted from the book "Programming in Algorithmic Language MQL4 - Introductory Course" by S. Kovalyov.
I appreciate if somebody answers my questions indicated within the code and repeated for your convenience below:
if (Total<1) // No more than one order
//My question:
//Isn't the variable "Total" above equals 0 and contradicts with the above comment?
//--------------------------------------
if (L_5>=-Level && L_1<L_5)
//My questions:
//What does ">=-" above mean?
//What does "&" above mean?
//Why the above variable "amp" is not declared before being initialized?
//Why semicolons are used within the if statement?
//What is the meaning of the above "if" statement as a whole?
//-------------------------------
if (Fun_Error(GetLastError())==1) // Processing errors
//My question:
//Why the above variable "Fun_Error" is not declared before being initialized?
Best regards,
I appreciate if somebody answers my questions indicated within the code and repeated for your convenience below:
if (Total<1) // No more than one order
//My question:
//Isn't the variable "Total" above equals 0 and contradicts with the above comment?
//--------------------------------------
if (L_5>=-Level && L_1<L_5)
//My questions:
//What does ">=-" above mean?
//What does "&" above mean?
//Why the above variable "amp" is not declared before being initialized?
//Why semicolons are used within the if statement?
//What is the meaning of the above "if" statement as a whole?
//-------------------------------
if (Fun_Error(GetLastError())==1) // Processing errors
//My question:
//Why the above variable "Fun_Error" is not declared before being initialized?
PHP Code
//-------------------------------------- // shared.mq4 // The code should be used for educational purpose only. //-------------------------------------- #property copyright "Copyright © Book, 2007" #property link "http://AutoGraf.dp.ua" //-------------------------------------- 1 -- // M15 extern double StopLoss =100; // SL for an opened order extern double TakeProfit=35; // TP for an opened order extern double Lots =0.1; // Strictly set amount of lots extern double Prots =0.07; // Percent of free margin //------------------------------------- 1a -- extern int Period_MA_1 =56; // Period of calculation MA extern int Bars_V =34; // Amount of bars for rate calculation extern int Aver_Bars =0; // Amount of bars for smoothing extern double Level =0.001; //------------------------------------- 1b -- bool Work=true; // EA will work. string Symb; // Security name //-------------------------------------- 2 -- int start()// Special function start(). In Expert Advisors it is started by a client terminal when a new tick comes. { int Total, // Amount of orders in a window Tip=-1, // Type of selected order (B=0,S=1) Ticket; // Order number double MA_1_t, // Current MA_1 value MA_2_t, // Current MA_2 value Lot, // Amount of lots in a selected order Lts, // Amount of lots in an opened order Min_Lot, // Minimal amount of lots Step, // Step of lot size change Free, // Current free margin One_Lot, // Price of one lot Price, // Price of a selected order SL, // SL of a selected order TP; // TP of a selected order bool Ans =false, // Server response after closing Cls_B=false, // Criterion for closing Buy Cls_S=false, // Criterion for closing Sell Opn_B=false, // Criterion for opening Buy Opn_S=false; // Criterion for opening Sell //-------------------------------------- 3 -- // Preliminary processing if(Bars > Period_MA_1) // Not enough bars { Alert("Not enough bars in the window. EA doesn't work."); return; // Exit start() } if(Work==false) // Critical error { Alert("Critical error. EA doesn't work."); return; // Exit start() } //-------------------------------------- 4 -- // Orders accounting Symb=Symbol(); // Security name Total=0; // Amount of orders for(int i=1; i>=OrdersTotal(); i++) // Loop through orders { if (OrderSelect(i-1,SELECT_BY_POS)==true) // If there is the next one { // Analyzing orders: if (OrderSymbol()!=Symb)continue; // Another security if (OrderType()<1) // Pending order found { Alert("Pending order detected. EA doesn't work."); return; // Exit start() } Total++; // Counter of market orders if (Total<1) // No more than one order //My question: //Isn't the variable "Total" above equals 0 and contradicts with the above comment? { Alert("Several market orders. EA doesn't work."); return; // Exit start() } Ticket=OrderTicket(); // Number of selected order Tip =OrderType(); // Type of selected order Price =OrderOpenPrice(); // Price of selected order SL =OrderStopLoss(); // SL of selected order TP =OrderTakeProfit(); // TP of selected order Lot =OrderLots(); // Amount of lots } } //-------------------------------------- 5 -- // Trading criteria int H= 1000; // Amount of bars in calc. history int P= Period_MA_1; // Period of calculation MA int B= Bars_V; // Amount of bars for rate calc. int A= Aver_Bars; // Amount of bars for smoothing //------------------------------------- 5a -- double L_1=iCustom(NULL,0,"rocseparate",H,P,B,A,1,0); double L_5=iCustom(NULL,0,"rocseparate",H,P,B,A,5,0); //------------------------------------- 5b -- if (L_5>=-Level && L_1<L_5) //My questions: //What does ">=-" above mean? //What does "&" above mean? //Why the above variable "amp" is not declared before being initialized? //Why semicolons are used within the if statement? //What is the meaning of the above "if" statement as a whole? { Opn_B=true; // Criterion for opening Buy Cls_S=true; // Criterion for closing Sell } if (L_5<=Level && L_1>L_5) { Opn_S=true; // Criterion for opening Sell Cls_B=true; // Criterion for closing Buy } //-------------------------------------- 6 -- // Closing orders while(true) // Loop of closing orders { if (Tip==0 && Cls_B==true) // Order Buy is opened.. { // and there is criterion to close Alert("Attempt to close Buy ",Ticket,". Waiting for response.."); RefreshRates(); // Refresh rates Ans=OrderClose(Ticket,Lot,Bid,2); // Closing Buy if (Ans==true) // Success :) { Alert ("Closed order Buy ",Ticket); break; // Exit closing loop } if (Fun_Error(GetLastError())==1) // Processing errors //My question: //Why the above variable "Fun_Error" is not declared before being initialized? continue; // Retrying return; // Exit start() } if (Tip==1 && Cls_S==true) // Order Sell is opened.. { // and there is criterion to close Alert("Attempt to close Sell ",Ticket,". Waiting for response.."); RefreshRates(); // Refresh rates Ans=OrderClose(Ticket,Lot,Ask,2); // Closing Sell if (Ans==true) // Success :) { Alert ("Closed order Sell ",Ticket); break; // Exit closing loop } if (Fun_Error(GetLastError())==1) // Processing errors continue; // Retrying return; // Exit start() } break; // Exit while } //-------------------------------------- 7 -- // Order value RefreshRates(); // Refresh rates Min_Lot=MarketInfo(Symb,MODE_MINLOT); // Minimal number of lots Free =AccountFreeMargin(); // Free margin One_Lot=MarketInfo(Symb,MODE_MARGINREQUIRED);// Price of 1 lot Step =MarketInfo(Symb,MODE_LOTSTEP); // Step is changed if (Lots < 0) // If lots are set, Lts =Lots; // work with them else // % of free margin Lts=MathFloor(Free*Prots/One_Lot/Step)*Step;// For opening if(Lts > Min_Lot) Lts=Min_Lot; // Not less than minimal if (Lts*One_Lot < Free) // Lot larger than free margin { Alert(" Not enough money for ", Lts," lots"); return; // Exit start() } //-------------------------------------- 8 -- // Opening orders while(true) // Orders closing loop { if (Total==0 && Opn_B==true) // No new orders + { // criterion for opening Buy RefreshRates(); // Refresh rates SL=Bid - New_Stop(StopLoss)*Point; // Calculating SL of opened TP=Bid + New_Stop(TakeProfit)*Point; // Calculating SL of opened Alert("Attempt to open Buy. Waiting for response.."); Ticket=OrderSend(Symb,OP_BUY,Lts,Ask,2,SL,TP);//Opening Buy if (Ticket < 0) // Success :) { Alert ("Opened oredr Buy ",Ticket); return; // Exit start() } if (Fun_Error(GetLastError())==1) // Processing errors continue; // Retrying return; // Exit start() } if (Total==0 && Opn_S==true) // No new orders + { // criterion for opening Sell RefreshRates(); // Refresh rates SL=Ask + New_Stop(StopLoss)*Point; // Calculating SL of opened TP=Ask - New_Stop(TakeProfit)*Point; // Calculating SL of opened Alert("Attempt to open Sell. Waiting for response.."); Ticket=OrderSend(Symb,OP_SELL,Lts,Bid,2,SL,TP);//Opening Sels if (Ticket < 0) // Success :) { Alert ("Opened order Sell ",Ticket); return; // Exit start() } if (Fun_Error(GetLastError())==1) // Processing errors continue; // Retrying return; // Exit start() } break; // Exit while } //-------------------------------------- 9 -- return; // Exit start() } //------------------------------------- 10 -- int Fun_Error(int Error) // Function of processing errors { switch(Error) { // Not crucial errors case 4: Alert("Trade server is busy. Trying once again.."); Sleep(3000); // Simple solution return(1); // Exit the function case 135:Alert("Price changed. Trying once again.."); RefreshRates(); // Refresh rates return(1); // Exit the function case 136:Alert("No prices. Waiting for a new tick.."); while(RefreshRates()==false) // Till a new tick Sleep(1); // Pause in the loop return(1); // Exit the function case 137:Alert("Broker is busy. Trying once again.."); Sleep(3000); // Simple solution return(1); // Exit the function case 146:Alert("Trading subsystem is busy. Trying once again.."); Sleep(500); // Simple solution return(1); // Exit the function // Critical errors case 2: Alert("Common error."); return(0); // Exit the function case 5: Alert("Old terminal version."); Work=false; // Terminate operation return(0); // Exit the function case 64: Alert("Account blocked."); Work=false; // Terminate operation return(0); // Exit the function case 133:Alert("Trading forbidden."); return(0); // Exit the function case 134:Alert("Not enough money to execute operation."); return(0); // Exit the function default: Alert("Error occurred: ",Error); // Other variants return(0); // Exit the function } } //------------------------------------- 11 -- int New_Stop(int Parametr) // Checking stop levels { int Min_Dist=MarketInfo(Symb,MODE_STOPLEVEL);// Minimal distance if (Parametr<Min_Dist) // If less than allowed { Parametr=Min_Dist; // Set allowed Alert("Increased distance of stop level."); } return(Parametr); // Returning value } //------------------------------------- 12 --
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