Errors, bugs, questions - page 2753

[Igor Makanu]

Alexey Navoykov:
In C# the const specifier is used only for constant expressions calculated at the compilation stage, while C++ has an analog for it: constexpr,and MQL doesn't have it.

yes

it's generally a question of syntactic constructions of languages

in a natural language (in mathematics) a constant is... well it's kind of a constant! ))

In C++ a constant is a machine checking by the compiler for a constant in the scope (or lifetime) of a variable

In C# a constant has a syntactic meaning which is closer to the rules of a natural language

And that's what this discussion is about:

const MqlTick _Tick; // Текущий _Symbol-тик.

Imho, this construct fully complies with C++ syntax, or at least MQL4 had Bid and Ask and nobody doubted whether it was justified

Without demagogy we need the possibility to access current prices as quickly as possible. The profiler shows that permanent access to SymbolInfoDouble() and SymbolInfoTick() decreases the optimization speed

[Mihail Matkovskij]

Mihail Matkovskij:

How can I change the compiler?

I found out that the compiler is built into MetaEditor from the 900 build:https://www.mql5.com/ru/forum/21374

Then why is there a window with a line leading to the directory where VS is installed?

[Alexey Navoykov]

Igor Makanu:

Without demagogy, we need to be able to access current prices as quickly as possible. The profiler shows that constant calls to SymbolInfoDouble() and SymbolInfoTick() reduce optimization speed

Well, here's where it was suggested earlier to add the ability to pass NULL instead of the current symbol name. This could speed up work in special cases. In general, we need access through handles, not text values of symbols. But I think the developers are unlikely to go for such complication. The problem seems to be farfetched.

In the above mentioned measurements the cost was only 6% of the tester's idle run (without load). And in working code it will be an order of magnitude less. It's not worth paying attention to such trifles, and calling these functions more than once in a handler is an incorrect decision in itself.

[A100]

Alexey Navoykov:

Well here earlier it was suggested to add possibility to pass NULL instead of current symbol name. This could speed up work in special cases. But in general we need access via handles, not text values of characters. But I think developers are unlikely to go for such complication. And it is not worth it, it seems to me. The problem is rather farfetched.

It already works, but there is no acceleration (I checked) - apparently everything is already maximally accelerated or vice versa - for acceleration is still a long way off (please ask the developers to underline)

[fxsaber]

A100:

Therefore, for the sake of strictness, we should use Digits() instead of _Digits. Then formally and no logical contradiction occurs - Digits() is not bound by const modifier.

As far as I understood _Digits was needed for compatibility with MT4 - nothing more.

Forum on trading, automated trading systems and strategy testing

Bugs, bugs, questions

Ilyas, 2020.05.20 15:39

calling of Symbol() ALWAYS accesses to global variable _Symbol, as well as Digits(), Point(), Period(), GetLastError(), IsStopped(), UninitializeReason()

[Mihail Matkovskij]

Mihail Matkovskij:

During debugging and when the indicator is working itself, in the log, it suddenly writes Stack overflow. When debugging itself, the message "Critical error occurred, debugging stopped" pops up. Here is my similar thread:https://www.mql5.com/ru/forum/338301. But during compilation the compiler doesn't scold and everything goes fine. When debugging, it's impossible to determine at what point the program crashes.

Maybe it's the compiler? I'm not really interested in the compiler I'm using, but in my settings it looks like this:

I have VS installed, so I have this link in the settings. So the compiler is appropriate too...? But what compiler was there when I didn't have VS, I honestly didn't get into it. Maybe I should try to go back to that compiler and try to compile the project with it?

While I was looking for ways to solve the problem, with the arrival of another terminal update debugging worked properly. I managed to find errors. Some methods were looping and calling themselves. That's why the program crashed with the message "Stack overflow". But with the help of a working debugger I have managed to find all the problematic lines and fix them. I express my gratitude to the Developers for quick fixing of the bug with debugging!

[Koldun Zloy]

в естественном языке (в математике) константа это... ну как бы константа! ))

In C++, a constant is a machine check by the compiler on the constancy in the scope (or lifetime) of a variable.

In C++ as well as in MQL, a constant can be defined once at creation and never be changed again. Scopes have nothing to do with it.

It's not much different than in mathematics.

[Koldun Zloy]

Mihail Matkovskij:

I found out that the compiler is built into MetaEditor from the 900 build:https://www.mql5.com/ru/forum/21374

Then why this window with a line leading to the directory where VS is installed?

The VS compiler is used if you write a DLL.

[A100]

fxsaber:

Which once again confirms that there is no sense inusing _Digits,_Point , _Period, _LastError, etc.directly(and even _Symbol can be replaced by NULL). In fact, they must be declared as const volatile

And you, on the contrary, are suggesting to add

[fxsaber]

A100:

Which once again confirms that there is no point inusing _Digits,_Point , _Period, _LastError, etc.directly. And even _Symbol may be replaced with NULL.

And you, on the contrary, are offering to supplement this series.

The point is in the possibility to pass by reference.