Variable Scope Inside Loop?

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Hi,

for(int i=barsBack;i>=0;i--){
      bool MACrossedUp;
      int event;

      MACrossedUp=true;
      event=10;
}

I would expect both these variables to initialize to their default values (false, 0) in each for loop iteration, because I declare them inside the loop.

This is how other languages (like Java) would handle this.

But interestingly, both these variables preserve their changed values in each iteration, despite redeclaration in each iteration.

Can someone tell me why is this, or how does MQL handle this code?

Thanks,

JForex.

 

Seems buggy, yes...

If explicitly declared, it works.

//+------------------------------------------------------------------+
//| script program start function                                    |
//+------------------------------------------------------------------+
int start()
  {
   for(int i = 0; i < 5; i++){
      bool Bool;
      int  Int;
   
      Print("Bool = ", Bool, "  Int = ", Int);
   
      Bool = true;
      Int = i;
   }

   // EXPLICIT
   for(   i = 0; i < 5; i++){
      bool Bool1 = false;
      int  Int1 = 0;
   
      Print("Bool1 = ", Bool1, "  Int1 = ", Int1);
   
      Bool1 = true;
      Int1 = i;
   }
   return(0);
  }

Output

2009.05.24 02:26:47 test AUDCHF,H1: uninit reason 0
2009.05.24 02:26:47 test AUDCHF,H1: Bool1 = 0  Int1 = 0
2009.05.24 02:26:47 test AUDCHF,H1: Bool1 = 0  Int1 = 0
2009.05.24 02:26:47 test AUDCHF,H1: Bool1 = 0  Int1 = 0
2009.05.24 02:26:47 test AUDCHF,H1: Bool1 = 0  Int1 = 0
2009.05.24 02:26:47 test AUDCHF,H1: Bool1 = 0  Int1 = 0
2009.05.24 02:26:47 test AUDCHF,H1: Bool = 1  Int = 3
2009.05.24 02:26:47 test AUDCHF,H1: Bool = 1  Int = 2
2009.05.24 02:26:47 test AUDCHF,H1: Bool = 1  Int = 1
2009.05.24 02:26:47 test AUDCHF,H1: Bool = 1  Int = 0
2009.05.24 02:26:47 test AUDCHF,H1: Bool = 0  Int = 0
2009.05.24 02:26:47 test AUDCHF,H1: loaded successfully
2009.05.24 02:26:38 Compiling 'test'
 
phy wrote >>

Seems buggy, yes...

If explicitly declared, it works.

Output

Right, thats buggy.

It seems like a 2 pass compiler. In pass 1 it sees all declarations in a function, sticks them in memory. If it finds something declared in the memory, it will not redeclare again. So next time it sees a declaration within the loop, it will not redeclare, but use from memory.

There are some other oddities as well. Arrays are automatically static (sticky). Try it.

JForex.

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