arrays in mql4

i'm new to the mql4 language (but not to programming), and i seem to be getting an error at line 3 of my code:

int numOfBars = 20;
int LowCount = 0; //Number of lows
int LowPositions[numOfBars]; //Array to hold the positions of the lows

Those variables arent initialized at the point. numOfBar has no value. After start() you can ArrayResize(LowPositions, numOfBars); to size it until then just...

int numOfBars = 20;
int LowCount = 0; //Number of lows
int LowPositions[1]; //Array to hold the positions of the lows

int start()
{
ArrayResize(LowPositions, numOfBars);
.....

I would suggest doing the array resize in init() if numOfBars doesnt change during operation or only call it when numOfBars really has changed so it doesn't call this function on every tick. ArrayResize() is quite expensive, especially for bigger arrays.