112 lines
2.9 KiB
MQL5
112 lines
2.9 KiB
MQL5
//+------------------------------------------------------------------+
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//| Structs.mq5 |
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//| Copyright 2021, MetaQuotes Ltd. |
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//| https://www.mql5.com |
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//+------------------------------------------------------------------+
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#define N_COEF 3
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struct Settings
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{
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datetime start;
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int barNumber;
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ENUM_APPLIED_PRICE price;
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int components;
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};
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struct Result
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{
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// public: is assumed by default for structs
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double probability;
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double coef[N_COEF];
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int direction;
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private:
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string status;
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public:
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void Result()
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{
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static int count = 0;
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Print(__FUNCSIG__, " ", ++count);
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status = "ok";
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}
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void Result(string s)
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{
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static int count = 0;
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Print(__FUNCSIG__, " ", ++count);
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status = s;
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}
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void ~Result()
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{
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static int count = 0;
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Print(__FUNCSIG__, " ", ++count);
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}
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void print()
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{
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Print(probability, " ", direction, " ", status);
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ArrayPrint(coef);
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}
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};
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//+------------------------------------------------------------------+
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//| Some calculations stub |
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//+------------------------------------------------------------------+
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Result calculate(Settings &settings)
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{
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// adjust inputs: read and write struct members
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if(settings.barNumber > 1000)
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{
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settings.components = (int)(MathSqrt(settings.barNumber) + 1);
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}
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// ...
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// simulate a result
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Result r;// = {}; // 'r' - cannot be initialized with initializer list
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r.probability = 0.5;
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r.direction = +1;
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// error:
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// cannot access to private member 'status' declared in struct 'Result'
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// r.status = "message";
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for(int i = 0; i < N_COEF; i++) r.coef[i] = i + 1;
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return r;
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}
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//+------------------------------------------------------------------+
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//| Script program start function |
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//+------------------------------------------------------------------+
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void OnStart()
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{
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Settings s = {D'2021.01.01', 1000, PRICE_CLOSE, 8};
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// error: '{' - parameter conversion not allowed
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// s = {D'2021.01.01', 1000, PRICE_CLOSE, 8};
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/* ok: member-wise assignment
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s.start = D'2021.01.01';
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s.barNumber = 1000;
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s.price = PRICE_CLOSE;
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s.components = 8;
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*/
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Result r = calculate(s);
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// Print(r); // error: 'r' - objects are passed by reference only
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// Print(&r); // error: 'r' - class type expected
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r.print();
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// will output:
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// 0.5 1 ok
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// 1.00000 2.00000 3.00000
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Result r2("n/a");
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r2 = r; // ok: full member-wise copy
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r2.print();
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// will output the same data:
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// 0.5 1 ok
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// 1.00000 2.00000 3.00000
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Print(offsetof(Result, status)); // 36
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}
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