can we use Pointers like in C++ | Forex Factory

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can we use Pointers like in C++

  • #1
  • First Post: Nov 9, 2009 2:41pm Nov 9, 2009 2:41pm
Hey everyone,

Simple question for all the programmers here...

are we able to use pointers in MQL4 like in C... you know like if we wanted to pass a variable through to a method so that we wouldn t have to change the method everytime...

If so ... whats the syntax cause * and & ain t doin it for me

Thanks
  • #2
  • Edited 3:21pm Nov 9, 2009 3:18pm | Edited 3:21pm
not allowed
ps: pass the variable in the parm string
iRtn - SomeFunction(parm1, 2,etc)

int SomeFunction(parm1, 2,etc)
{
whatever
}
  • #3
  • Nov 9, 2009 3:58pm Nov 9, 2009 3:58pm
Thanks kenz,

not sure what your trying to say after but i'm sure its an alternative... could you elaborate a bit... does anyone know another way to do this?
  • #4
  • Nov 9, 2009 5:21pm Nov 9, 2009 5:21pm
or use globals whose scope is your entire indicator, or if you are passing from one indi to another use Globals.
The parm method I showed is standard variable passing technique. I expect one of the more advanced programmers here can make me wrong and show a way to use pointers by fooling the compiler or something, but this is what I use and it works.
  • #5
  • Nov 9, 2009 10:55pm Nov 9, 2009 10:55pm
Ken Thanks for the suggestion;

I'm embarrassed to say that I still do not understand your "parm method" could you provide a short example? are you saying your just pasing a string? if so how do i set it as the variable within the function?

THanks again for your help
  • #6
  • Nov 10, 2009 1:46pm Nov 10, 2009 1:46pm
Quoting Rbi
Ken Thanks for the suggestion;

I'm embarrassed to say that I still do not understand your "parm method" could you provide a short example? are you saying your just pasing a string? if so how do i set it as the variable within the function?
What are you trying to do? Your original post was quite unclear.

Do you want to pass variables by reference? this can be done:

Inserted Code
void foobar(int& foo, double& bar[]){
  foo = 42;
  bar[2] = 3;
}

int start(){
  int a;
  double b[100];

  foobar(a, b);  // fill the variables

  Print(a);
  Print(b[2]);
}

Or are you trying to get function pointers?

Do you want to implement callbacks or even pass complete functions around like closures? Unfortunately this is not possible. MQL is a very poor language missing most of the useful features known from other programing langiuages.
  • #7
  • Edited 11:53am Nov 11, 2009 9:46am | Edited 11:53am
Hey 7 bit...

I was trying to get function pointers but what you gave me is pretty much the same thing... Ken if this is what you meant, works great for what I am using it for...

Thanks guys
  • #8
  • Nov 11, 2009 12:20pm Nov 11, 2009 12:20pm
Thanks 7bit. I always have trouble with the call by reference, those little "&" thingys. It's best to find samples and learn from them. There is much sample code in the trading systems section, and on forex tsd, and code base.
  • #9
  • Last Post: Nov 13, 2009 5:28am Nov 13, 2009 5:28am
Quoting Kenz987
Thanks 7bit. I always have trouble with the call by reference, those little "&" thingys. It's best to find samples and learn from them.
This syntax isn't mentioned in the MQL4 reference, at least not in the "functions" section where it would belong. I found it by accident while looking into the help for some of the array functions.
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