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Beginner EA questions?

  • #1
  • First Post: Jan 21, 2007 4:18pm Jan 21, 2007 4:18pm
I am working on my first EA, and there are some things I'm not clear on. I'm reading the tutorial by Coder's Guru and I've also searched the MetaEditor's on-line help. I would like more info on the following.

1)What is Point for? This is apparently "the point value of the current bar (usually 0.0001)". Wouldn't the point value be the price? It's used in OrderSend: Ask+TakeProfit*Point, Ask-StopLoss*Point. Why do you multiply by Point here? Couldn't you set TakeProfit to 0.0020 and then in OrderSend you would write Ask+TakeProfit to specify the Take Profit price?

2)What is Slippage in OrderSend() function? I know what slippage is - the difference between the price when you tried to open or close an order and the price you were filled at. But what are you telling the OrderSend function when you specify a slippage amount?

3)What is difference between Symbol() and OrderSymbol()? I know OrderSymbol() is used after using OrderSelect and Symbol() is used in OrderSend(). Is that the extent of the difference? Is symbol() used anywhere else?

4)init() and deinit(). Init() is where you can initialize global variables or you can just initialize them when you declare them. Correct?
What is deinit() for? Is it a necessary part of every EA? Can I delete my deinit()?

Thanks.
  • #2
  • Edited 9:44pm Jan 21, 2007 9:08pm | Edited 9:44pm
  •  tesla
  • | Joined Oct 2006 | Status: Friendly Neighborhood Programmer | 533 Posts
Quoting locutus
1)What is Point for? This is apparently "the point value of the current bar (usually 0.0001)". Wouldn't the point value be the price? It's used in OrderSend: Ask+TakeProfit*Point, Ask-StopLoss*Point. Why do you multiply by Point here? Couldn't you set TakeProfit to 0.0020 and then in OrderSend you would write Ask+TakeProfit to specify the Take Profit price?
You could absolutely just set takeprofit to 0.0020, but it's less flexible that way. What if you want your EA to work on USDJPY and EURUSD? USDJPY only has two decimal places of precision so 0.0020 wouldn't work. If you had takeprofit set to 20 for both and multiplied by point, you'd be all set. That doesn't mean it's wrong the way you're doing it, it's simply an explanation of why you see values multiplied by Point all over the place.


Quoting locutus
2)What is Slippage in OrderSend() function? I know what slippage is - the difference between the price when you tried to open or close an order and the price you were filled at. But what are you telling the OrderSend function when you specify a slippage amount?
The amount of requote you'll accept without the order being rejected.


Quoting locutus
3)What is difference between Symbol() and OrderSymbol()? I know OrderSymbol() is used after using OrderSelect and Symbol() is used in OrderSend(). Is that the extent of the difference? Is symbol() used anywhere else?
Symbol() returns the pair for the chart the EA is attached to. OrderSymbol() returns the pair for the order. Some EAs open orders on multiple pairs simultaneously, or you might have the same EA running on more than one chart. If this is the case, being able to check both Symbol() and OrderSymbol() can be important.


Quoting locutus
4)init() and deinit(). Init() is where you can initialize global variables or you can just initialize them when you declare them. Correct?
What is deinit() for? Is it a necessary part of every EA? Can I delete my deinit()?
Correct on init(). init() is a great place to do some error checking to insure that the extern values being used make sense.

I rarely need deinit(). If my indicator or EA draws objects on the chart, I delete them in deinit(). If I want to make sure I don't leave orphan orders open, I clean them up in deinit(). If you don't need to do anything when the EA is being deactivated, you can safely delete or ignore the deinit() function.
  • #3
  • Jan 21, 2007 11:21pm Jan 21, 2007 11:21pm
Thanks! Very clear answers.
  • #4
  • Jan 22, 2007 12:52am Jan 22, 2007 12:52am
You and everyone should also be aware that if you're looking at old EA's you've downloaded you might see a time function called "CurTime()" to find the current time.

If you've upgraded to build 200 or 201, you can't use "CurTime()" anymore. The new name for it is "TimeCurrent()"

Build 201 won't recognize the old CurTime() but you'll probably see it in a lot of recent and older EA's because CurTime () has to be used in Build 198 or older.

In Build 201, go into your MetaEditor, go to the navigator, click on dictionary, go to the bottom and you should see a file called obsolete functions. This will tell you what things they've changed in Build 201 that could affect the performance of an EA.
  • #5
  • Jan 22, 2007 2:08am Jan 22, 2007 2:08am
Hi I have modified a MagicNumber example as follows; int MagicNumber = 101030;

extern double Profit = 100;
extern double Loss = -100;

//+------------------------------------------------------------------
int init()
{
return(0);
}

int deinit()
{
return(0);
}
int start()
{
int cnt, ticket, total,n;

if(Bars<100) {Print("bars less than 100"); return(0);}

total = OrdersTotal();

if(total < 1)
{
OrderSend("GBPCHF",OP_BUY,0.1,Ask,5,0,Ask+100*Point,"Hedge demo",MagicNumber,0,Green);
OrderSend("EURJPY",OP_BUY,0.1,Ask,5,0,Ask+100*Point,"Hedge demo",MagicNumber,0,Green);
OrderSend("EURGBP",OP_SELL,0.1,Bid,5,0,Bid-100*Point,"Hedge demo",MagicNumber,0,Red);
OrderSend("CHFJPY",OP_SELL,0.1,Bid,5,0,Bid-100*Point,"Hedge demo",MagicNumber,0,Red);
return(0);
}

ProfitLossMonitor();

return(0);
}


void ProfitLossMonitor()
{
int total = OrdersTotal();
double MyCurrentProfit=0;
for (int cnt = 0 ; cnt < total ; cnt++)
{
OrderSelect(cnt,SELECT_BY_POS,MODE_TRADES);
if (OrderMagicNumber() == MagicNumber)
MyCurrentProfit += OrderProfit();
}

if(MyCurrentProfit>=Profit)
CloseAll();

if(MyCurrentProfit<=Loss)
CloseAll();

}

void CloseAll()
{
int total = OrdersTotal();
for (int cnt = 0 ; cnt < total ; cnt++)
{
OrderSelect(cnt,SELECT_BY_POS,MODE_TRADES);
if (OrderMagicNumber() == MagicNumber)
if(OrderType()==OP_BUY)
OrderClose(OrderTicket(),OrderLots(),Bid,5,Violet);
if(OrderType()==OP_SELL)
OrderClose(OrderTicket(),OrderLots(),Ask,5,Violet);
}
}

I attached this ea to GBPCHF chart and only GBPCHF is traded the other pairs in the EA is not traded.
what did I missed out?
Thanks
  • #6
  • Jan 22, 2007 8:32am Jan 22, 2007 8:32am
Quoting kmrunner
If you've upgraded to build 200 or 201, you can't use "CurTime()" anymore. The new name for it is "TimeCurrent().Build 201 won't recognize the old CurTime() "
Wrong, you can use it, but it will be show as normal text...
Quote from help file :
"
In further development of MQL4, some functions were renamed and moved from one group to another in order to systematize them better. The old function names are not highlighted or linked to the MetaEditor Dictionary. The old function names can be used since the compiler will accept them in a proper way. However, we strongly recommend to use the new names.
"
You can use it, but its not wise since there is a new version/name for it...
Logic, they will not destroy old Source code just like that...
But new Code should use TimeCurrent().
Sorry for my bad english translation
  • #7
  • Edited 5:09pm Jan 22, 2007 3:34pm | Edited 5:09pm
  •  tesla
  • | Joined Oct 2006 | Status: Friendly Neighborhood Programmer | 533 Posts
Fxzt,

On Blackberry, short reply. More when home.

All orders places at GBPCHF price with only 5 pip slippage. No way USDJPY or other orders will fill.

Edit
Okay... now that I'm in front of a full-sized keyboard, I can give more specific info. Here are the orders from your code:
PHP Code
OrderSend("GBPCHF",OP_BUY,0.1,Ask,5,0,Ask+100*Point,"Hedge demo",MagicNumber,0,Green);
OrderSend("EURJPY",OP_BUY,0.1,Ask,5,0,Ask+100*Point,"Hedge demo",MagicNumber,0,Green);
OrderSend("EURGBP",OP_SELL,0.1,Bid,5,0,Bid-100*Point,"Hedge demo",MagicNumber,0,Red);
OrderSend("CHFJPY",OP_SELL,0.1,Bid,5,0,Bid-100*Point,"Hedge demo",MagicNumber,0,Red);
Notice that they're all referencing Bid or Ask. That's not a problem with the first order for GBPCHF, since the EA is on a chart for GBPCHF and the values returned from Ask make sense. When you hit the second order and you're still referencing the GBPCHF Ask, the order gets rejected because the EURJPY Ask price is more than 5 pips (value you specified for slippage) away from the price you specified (GBPCHF Ask price). Make sense?
  • #8
  • Jan 23, 2007 11:58am Jan 23, 2007 11:58am
Thanks Tesla,
How do I set in the EA to get the other pair ask price, ...?
  • #9
  • Jan 23, 2007 12:44pm Jan 23, 2007 12:44pm
  •  tesla
  • | Joined Oct 2006 | Status: Friendly Neighborhood Programmer | 533 Posts
Quoting fxzt
Thanks Tesla,
How do I set in the EA to get the other pair ask price, ...?
For other pairs, use the MarketInfo function:
double dBidPrice = MarketInfo("EURUSD",MODE_BID);
double dAskPrice = MarketInfo("EURUSD",MODE_ASK);

You can get quite a bit of information using MarketInfo depending on the value of the second param.
  • #10
  • Jan 23, 2007 5:11pm Jan 23, 2007 5:11pm
fxzt and sypultraz: If you have a question you're supposed to start your own thread. What you're both doing is called hijacking a thread. Well, actually sypultraz, you only tried to hijack a thread and fxzt, you actually succeeded quite well unfortunately. How lazy are you if you can't be bothered to leave a thread and return to the main page and start your own thread?
  • #11
  • Jan 23, 2007 5:22pm Jan 23, 2007 5:22pm
locutus(Or merlin),
if you report my last post(removed) as bad or kmrunner post as bad, Thanks....
Sorry for my bad english translation
  • #12
  • Jan 23, 2007 10:21pm Jan 23, 2007 10:21pm
locutus, new to forum so thinking that this tread is for beginner EA questions, therefore I posted my question here. Anyway didn't intend to hijack this tread. Will start another tread when I have other questions. Thanks for the advise.



Quoting locutus
fxzt and sypultraz: If you have a question you're supposed to start your own thread. What you're both doing is called hijacking a thread. Well, actually sypultraz, you only tried to hijack a thread and fxzt, you actually succeeded quite well unfortunately. How lazy are you if you can't be bothered to leave a thread and return to the main page and start your own thread?
  • #13
  • Jan 24, 2007 8:03pm Jan 24, 2007 8:03pm
Quoting Zeuzere
locutus(Or merlin),
if you report my last post(removed) as bad or kmrunner post as bad, Thanks....
I have no intention of reporting anything. Offering unsolicited advise as you and Kmrunner did is one thing. So long as it doesn't get out of hand, any advise is good advise. Asking questions unrelated to the thread topic, however, is totally different. Questions tend to get answered and the result is a thread with a whole lot of posts that are unrelated to the thread topic. Thanks for the info on TimeCurrent().
  • #14
  • Last Post: Jan 24, 2007 11:09pm Jan 24, 2007 11:09pm
I totally agree,
and on my first post, did not want to give info, but wanted to make things clear...
Many people, make false affirmation(With good attention most of the time) or do not explain correctly.
Sorry, if it was out of scope.

Quoting locutus
I have no intention of reporting anything. Offering unsolicited advise as you and Kmrunner did is one thing. So long as it doesn't get out of hand, any advise is good advise. Asking questions unrelated to the thread topic, however, is totally different. Questions tend to get answered and the result is a thread with a whole lot of posts that are unrelated to the thread topic. Thanks for the info on TimeCurrent().
Sorry for my bad english translation
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