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Any questions from newcomers on MQL4 and MQL5, help and discussion on algorithms and codes - page 1236

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Andrey Sokolov:

Greetings. Could you please tell me something?

Is it possible to get the name of a variable instead of its value? For example, print a variable name.

#define PRINTVAR(x) Print(" " ##x); Print(x)
void OnStart()
  {
      long anyvar=(long)TimeLocal();
      PRINTVAR(anyvar);
  
  }

result:

2020.08.24 14:46:05.394    test (USDCHF,H1)     anyvar
2020.08.24 14:46:05.394    test (USDCHF,H1)    1598280365

Possibly a feature from unpublished :-) similar to "C", but not yet usable

Andrey Sokolov:

You need to get the name of the variable itself.

Without knowing the name, and without any distinguishing features, this cannot be done. You can, for example, get the names of all variables equal to 5 and print their names, found, printed. Or names of all string variables. But in any case it is a variable enumeration.

Maxim Kuznetsov thank you
Andrey Sokolov:
Maxim Kuznetsov Thanks


Yes, it's also a question of selecting a variable by name.

For example, there are variables a1, a2, a3, a4, a5, etc. You have to search through these variables too, choose which one has "a" and 5, and use it.

then there is almost no way. Variable names are only accessible from the preprocessor (#macros).

We must change the internal logic, e.g. use an object hash array of names instead of variables. Then both key and value are available at once. Or use SQLite in case of long term storage. Or combine them :-)

But it is so, without knowledge of algorithm, advice in vain.

Andrey Sokolov:

Yes, it's also a question of selecting a variable by name.

For example, there are variables a1, a2, a3, a4, a5, etc. We need to enumerate these variables too, choose which one has "a" and 5, and use it.

Write the names in an array and go through the array.

Good day all! My question is about MT4 tester, mql4 language
Please tell me what is my mistake when initialising an array. I have created a one-dimensional array with 750 elements. I initialized all 750 elements with value 50.0.

It means that on the first and following ticks, the first array item with index 0 must have value 50.0 and the last array item with index 749 must have value 50.0.

In fact it turns out that the last array item has value 0. And the first one, as it should be, is 50.0.

The question. How to make all values of the array (including the last one) have value 50.0 after initialization

Here is my code

double S_L[750]={50.0};

void OnTick()
{
if (Day()==4&&Month()==1&&Year()==2010&&Hour()==0&&Minute()==0)

Print("=========================749======= ",S_L[749]," =0= ",S_L[0]);

}

At the bottom of the Print() value from the journal

2020.08.24 17:43:55.427 GBPUSD,M1: 52255 tick events (1440 bars, 53256 bar states) processed in 0:00:00.047 (total time 0:00:02.422)

2020.08.24 17:43:55.407 2010.01.04 00:00:53 TESTER(B.ORG) GBPUSD,M1: =========================749======= 0 = 0= 50

2020.08.24 17:43:55.407 2010.01.04 00:00:52 TESTER(B.ORD) GBPUSD,M1: =========================749======= 0 = 0= 50

2020.08.24 17:43:55.407 2010.01.04 00:00:50 TESTER(B.ORD) GBPUSD,M1: =========================749======= 0 = 0= 50

2020.08.24 17:43:55.407 2010.01.04 00:00:47 TESTER(B.ORD) GBPUSD,M1: =========================749======= 0 = 0= 50

2020.08.24 17:43:55.407 2010.01.04 00:00:45 TESTER(B.ORD) GBPUSD,M1: =========================749======= 0 = 0= 50

2020.08.24 17:43:55.407 2010.01.04 00:43 TESTER(B.ORD) GBPUSD,M1: =========================749======= 0 = 0= 50

2020.08.24 17:43:55.407 2010.01.04 00:00:41 TESTER(B.ORD) GBPUSD,M1: =========================749======= 0 = 0= 50

2020.08.24 17:43:55.407 2010.01.04 00:00:40 TESTER(B.ORD) GBPUSD,M1: =========================749======= 0 = 0= 50

2020.08.24 17:43:55.407 2010.01.04 00:00:37 TESTER(B.ORD) GBPUSD,M1: =========================749======= 0 = 0= 50

2020.08.24 17:43:55.407 2010.01.04 00:00:35 TESTER(B.ORD) GBPUSD,M1: =========================749======= 0 = 0= 50

2020.08.24 17:43:55.407 2010.01.04 00:00:32 TESTER(B.ORD) GBPUSD,M1: =========================749======= 0 = 0= 50

2020.08.24 17:43:55.407 2010.01.04 00:00:30 TESTER(B.ORD) GBPUSD,M1: =========================749======= 0 = 0= 50

2020.08.24 17:43:55.407 2010.01.04 00:00:28 TESTER(B.ORD) GBPUSD,M1: =========================749======= 0 = 0= 50

2020.08.24 17:43:55.407 2010.01.04 00:00:26 TESTER(B.ORD) GBPUSD,M1: =========================749======= 0 = 0= 50

2020.08.24 17:43:55.407 2010.01.04 00:00:25 TESTER(B.ORD) GBPUSD,M1: =========================749======= 0 = 0= 50

2020.08.24 17:43:55.407 2010.01.04 00:00:22 TESTER(B.ORD) GBPUSD,M1: =========================749======= 0 = 0= 50

2020.08.24 17:43:55.407 2010.01.04 00:00:20 TESTER(B.ORD) GBPUSD,M1: =========================749======= 0 = 0= 50

2020.08.24 17:43:55.407 2010.01.04 00:00:17 TESTER(B.ORD) GBPUSD,M1: =========================749======= 0 = 0= 50

2020.08.24 17:43:55.407 2010.01.04 00:00:15 TESTER(B.ORD) GBPUSD,M1: =========================749======= 0 = 0= 50

2020.08.24 17:43:55.407 2010.01.04 00:00:13 TESTER(B.ORD) GBPUSD,M1: =========================749======= 0 = 0= 50

2020.08.24 17:43:55.407 2010.01.04 00:00:11 TESTER(B.ORD) GBPUSD,M1: =========================749======= 0 = 0= 50

2020.08.24 17:43:55.407 2010.01.04 00:00:10 TESTER(B.ORD) GBPUSD,M1: =========================749======= 0 = 0= 50

2020.08.24 17:43:55.407 2010.01.04 00:00:07 TESTER(B.ORD) GBPUSD,M1: =========================749======= 0 = 0= 50

2020.08.24 17:43:55.407 2010.01.04 00:00:05 TESTER(B.ORD) GBPUSD,M1: =========================749======= 0 = 0= 50

2020.08.24 17:43:55.407 2010.01.04 00:02 TESTER(B.ORD) GBPUSD,M1: =========================749======= 0 = 0= 50

2020.08.24 17:43:55.407 2010.01.04 00:00 TESTER(B.ORD) GBPUSD,M1: =========================749======= 0 = 0= 50

2020.08.24 17:43:55.385 2010.01.01 00:00:00 Tester(B.ORD.) test started


Thanks for the help


Документация по MQL5: Основы языка / Переменные
Документация по MQL5: Основы языка / Переменные
  • www.mql5.com
Переменные должны быть объявлены перед их использованием. Для идентификации переменных используются уникальные имена. Описания переменных используются для их определения и объявления типов. Описание не является оператором. Индексом массива может быть только целое число. Допускаются не более чем четырехмерные массивы. Нумерация элементов массива...
ANDREY:

Here's mine.

Where?))

Alexey Viktorov:

Where?)))

At the top in my edited post. Thanks for the response.

ANDREY:

Question. How can I make all values of my array (including the last one) have a value of 50.0 after initialisation?

int OnInit()
{
   ArrayInitialize(S_L, 50.0);
}
Igor Makanu:

Thanks for the tip. By the way I wanted to clarify..... In Kovalev's tutorial it says that the array can be initialized simultaneously with its declaration (as I did), without any special function. I know that Kovalev's tutorial is somewhat outdated. Q. Do I understand correctly, that now in mql4, arrays should be initialized only using a function?

ArrayInitialize(S_L, 50.0)

Thank you.

Документация по MQL5: Операции с массивами / ArrayInitialize
Документация по MQL5: Операции с массивами / ArrayInitialize
  • www.mql5.com
Функция ArrayResize() позволяет задать для массива размер с некоторым запасом для его будущего увеличения без физического перераспределения памяти. Это сделано для улучшения быстродействия, так как операции по распределению памяти...
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