MQL4 Problems checking current bid vs past tick | Forex Factory

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MQL4 Problems checking current bid vs past tick

  • #1
  • First Post: Oct 26, 2016 10:51am Oct 26, 2016 10:51am
Hello,

I know I coud ask the MQL4 community, but spreading my issure more widely will hopefully give me better answers. So here it is:

Inserted Code
double Bidtick[];
int i=0;
 
void OnTick()
{
 
i = i + 1;
ArraySetAsSeries(Bidtick,false);
 
Bidtick[i] = Bid;
 
   if(Bidtick[1]>Bidtick[2])
   {
         ...
   }
...
 
}


The problem that occours says "Critical error while running expert 'TickQuote EURUSD,H1'. Array out of range. Continue in debugger?".
I am new to MQL4 programming and so don't understand what to do. My goal is to check if the value of the bid price of the current (or very last respectively) tick is higher than then previous one.
May the Pip be with you.
  • #2
  • Oct 26, 2016 11:26am Oct 26, 2016 11:26am
Hi Chris,

you need to size the dynamic array Bidtick (dinamic arrays are empty when decalred)

Two ways (see mql help for reference):

a) SetIndexBuffer does everything auto and you have one array element for every single chart bar

b) ArrayResize, that is what you may need here, wich you can use to define the array size programmatically

Also remember arrays are zero-based so the first element is Bidtick[0] not Bidtick[1] and first iteration you have just one element so you can not make a two elements comparison (or you have to size accordingly)

Hope it helps, dynamic arrays are not the easiest piece to start if you have zero programmation knowledge.

What i can suggest is to go with debugger (and help guide) so you can understand how your code works and where and why it fails allowing you to develop your knowledge and skills
  • #3
  • Oct 26, 2016 12:37pm Oct 26, 2016 12:37pm
Thanks so far. I am not completely new to programming, I just have little experience with MQL4 espescially arrays.

What I did is just to implement:

Inserted Code
ArrayResize(Bidtick,100000,100000)

If I understood right, this should suffice.

Also, do you have links to quality explanations of MQL4 (or C++). I would like to learn more about that language. Unfurntunateley, books only explain basics - as much as I can get out of the MQL4 reference. I don't want to learn when to use specific functions or object but rather how and why to use them.
May the Pip be with you.
  • #4
  • Oct 26, 2016 12:49pm Oct 26, 2016 12:49pm
Why use an array?
Inserted Code
double PreviousTick=0;
void OnTick()
  {
   if(Bid>PreviousTick)
     {
      //current is larger than previous tick
     }
   PreviousTick=Bid;
Please Do Not PM Me With Coding Enquiries
  • #5
  • Oct 26, 2016 1:07pm Oct 26, 2016 1:07pm
Thanks! That's a lot simpler than arrays. I could have known. :-)
May the Pip be with you.
  • #6
  • Oct 26, 2016 1:30pm Oct 26, 2016 1:30pm
Quoting Chris1008
Thanks! That's a lot simpler than arrays. I could have known. :-)
Tought you had further elaboration to do ...

Better for you then
  • #7
  • Last Post: Oct 26, 2016 2:13pm Oct 26, 2016 2:13pm
For now, I need a genereal overview. And therefore the second idea is simply enough. Although your idea works advice works as well. I thank the two of you. Considering my problem (I observe ticks, not bars), adressing the i-th tick in an array would probably never give any positve result. The only thing I wanted, is an enumarator for upticks and downticks, so that I can compare them. Now I have it. :-)
May the Pip be with you.
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