80 lines
2.7 KiB
MQL5
80 lines
2.7 KiB
MQL5
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//+------------------------------------------------------------------+
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//| FuncTypedef.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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#property copyright "Copyright 2021, MetaQuotes Ltd."
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#property link "https://www.mql5.com"
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#property version "1.00"
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typedef double (*Calc)(double, double);
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Calc calc;
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//+------------------------------------------------------------------+
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//| Summation |
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//+------------------------------------------------------------------+
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double plus(double v1, double v2)
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{
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return v1 + v2;
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}
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//+------------------------------------------------------------------+
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//| Subtraction |
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//+------------------------------------------------------------------+
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double minus(double v1, double v2)
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{
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return v1 - v2;
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}
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//+------------------------------------------------------------------+
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//| Multiplication |
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//+------------------------------------------------------------------+
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double mul(double v1, double v2)
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{
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return v1 * v2;
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}
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//+------------------------------------------------------------------+
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//| Calculation by arbitrary function pointer |
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//+------------------------------------------------------------------+
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double calculator(Calc ptr, double v1, double v2)
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{
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if(ptr == NULL) return 0;
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return ptr(v1, v2);
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}
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//+------------------------------------------------------------------+
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//| Function pointer selector |
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//+------------------------------------------------------------------+
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Calc generator(ushort type)
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{
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Calc local;
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switch(type)
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{
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case '+':
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return plus;
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case '-':
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return minus;
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case '*':
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return mul;
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case '!':
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return local; // warning: possible use of uninitialized variable
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}
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return NULL;
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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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Print(calculator(plus, 1, 2)); // 3
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Print(calculator(minus, 1, 2)); // -1
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Print(calculator(calc, 1, 2)); // 0
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Print(calculator(generator('*'), 1, 2)); // 2
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Print(calculator(generator('!'), 1, 2)); // 0?
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}
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//+------------------------------------------------------------------+
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