3 Programming Function meanings?

Hello
Can Someone kindly explain in simple terms with an example the following issues:

1) What Does " Sleep(3000)" operator(or whatver u call it) do in betwen codes.
i have seen it many times in between if statements in many codes!

2) What does "break;" Function do?

3)What various types of Extern varaiables can be there? like double, Strings and their use?

4) Does MQL5 will be quite different from MQL4? i suppose its now released...any guess how much different?

if possible, can someone link to/post/pm some basic info abt Understanding, if not coding(as of now) MQL4.
i have lot of complex stuff/links etc... but time invested doesnt really solve the basic info i need (as of now)

Thanks in advance!
Regards

Ok ForexSaint I will take a try here.

1. Sleep, Is just a pause statement in the current operation. It can be used for different reasons and normally in a loop.
Think of it like the pause button on your dvd player. You stop the movie in its current spot to go make popcorn and then comeback to it. My wife loves this she can turn a 2 hour movie into an all night adventure...

Say you have a trade for a buy in your ea, but you don't want the buy performed right away. You could use the sleep function to pause the buy and then have it go back to your buy parameters in 60 seconds. So it would sleep(60) and then after that time go back to the trade function. There are other reasons for its use, but this is probably the most common type of thing.

2. Break, Is a change statement used mostly with the switch function. Say if you have some type of change in your trade or indicator you would use the switch function and then make a case statement for different parameters to be used due. The break statement would then tell the fisrt case to stop functioning and direct it to the second case function. I have also seen some programmers use it at the end of every function they code., before going onto the next function in the indicator, it doesn't hurt.

Best example I can think of here is a shi channel. If you got one take a look inside and you will see the switch. What it does is makes a switch for the period chart you are looking at, and tells it to use different parameters for each chart time period. Basically it tells the channel to use different fractal counts on each chart period. ( I have deleted that function on my Shi indicator).

3. Variables, Just about anything can become a variable. There are many types, extern int usually names a parameter to be used, say you want spacing. you would something like ..extern int y_spacing =10.. so you want your left/right spacing to be ten pixels, from something.
extern string.. you may be making a comment to explaing the spacing such as .. extern string note_1 =" y_spacing is sideways movement" or maybe you want to call a font type..extern string font_type="Arial"

You could extern bool to call a true or false function..extern bool change_color =True

You may have extern color=Green

Double is used as a smoothing process, say you are making a calculation that comes out in a fraction. The use of Double will smooth it to the actual decimal. You see it in alot of places it doesn't need to be, but it doesn't hurt if it is there. I guess it is easier to use it rather than to figure out if it is really needed.

You can also have global variables that will be at the beginning and used throughout the process and then you can have local variables that can be used within a specific function only.

Best thing to do is open up some codes and just follow them from start to finish and you will start to see the light, although my light does turn into a dim flashlight at times, it can be frustrating to code but then again fun when it eventually works.

You can start with the basic manual here http://book.mql4.com/. I do believe there is also a manual on ff if you use search. There is also another one from forex-tsd. com... You can also look my posts up and somewhere you will find I have posted the original course manual on ff.

As for mq5, as far as I have read it has not been published as of yet. It keeps getting a delay for whatever reason. It is supposed to be put out for programmers first, so they can get used to it. Then eventually the brokers will start to implement the platform.. I would guess still a year off before traders see it.

Post your questions there are some very generous and knowledgeable folks (much more than me) Hanover, Zen Loew, Ronald to name a few here that help, as time permits.

Good Luck
Tom

Thanks twj1usa for your time explaining all
yes coding is frustrating initially...Yes i will look into that link!
Thanks once again for explaining like that!

Best Regards

I'm going to elaborate a little on the use of the "break" statement.

It is mainly used to exit a conditional loop before it has reached the end of all its cycles (aka iterations).

Not just in switch structures, you may also use it inside a "for" loop, or a "while" loop.

within the MQL context, the most common use of break statement inside a loop would be when you want to look for a location on the chart (a particular candle) that matches a certain condition, and you just don't quite know where.

Let's assume you feel that location you're looking for is somewhere within the last 100 candles. but of cos you're not going to let it loop through 100 times even when the conditional was met in the first few candles.

here's a code example of how I'm looking for the most recently past candle where the stochastic is above 80.


so assuming at the second iteration, when i=2, the stochastic is already above 80, there's no need to go through the rest of the 98 cycles, the break statement will exit that entire for loop. This helps us get the EA or indicator to work more efficiently and reduce unnecessary runtime processing.

once you've understood the "break" statement. its probably a good idea to look at the "continue" statement as well.

regards,
Zen

Thanks for taking your time zen to explain it!
As i am new to MQL4 coding... got the basics...of above.... Though some things went abv head
Any way Cheers

Your posting sounds like you are generally not experienced in coding at all. This (for itself) is nothing you should be worried about since 95% of people using computers (in a productive way) dont use them to program them but rather use other people's programs to get their work done.

However: for being able to understand the cryptic words written in this strange looking alien language you see when you open the Metaeditor and look at the code of some Expert Advisor or Indicator you need to have an idea about the concept of "programming" per se, and this can only be achieved by learning what it actually means to "program a machine" and it can only be learned by actually trying to do it.

"Machine" in this context can be anything, it can for example mean a microprocessor and programming it would be done in assembler, it could alo mean "Microsoft Excel" and programming it would mean either putting formulas into spreadsheet cells or/and writing Visual Basic macros containing commands that should be executed at certain occasions in a certain order to make it [Excel, the machine] perform complicated things it wouldnt be able to do without your carefully crafted program. The machine could also be "Metatrader" and programming it would be writing Scripts, Experts and Indicators in mql4 which is the language of that machine, just like assembler is the language of the microcontroller and VB and formulas are the language of Excel.

Learning to program means find such a machine that can be easily programmed. A beginner should certainly not use a machine for which writing programs is a pain even for experienced programmers. You should start learning all these concepts in an environment where it is easy to create, run and debug your programs, where the machine will tell you what it didnt understand (and why) in a clear and friendly way. An environment where you can easily find out whats going on when something doesnt work as expected. Trying to learn programming Metatrader without ever having programmed anything before at all must be a frustrating experience.

An experienced programmer knows strategies how to narrow down the cause of an error even in unclear situations, he is prepared for all kinds of things that could go wrong, sometimes he can even smell it before it happens, just because of his rich experience.

You should really try to start learning programming with something that is easy for beginners, powerful enough to do even more complicated and useful stuff and through providing these properties is motivational and fun.

(I will leave room for other posters here to suggest suitable environmants, i personally strongly suggest Python. I dont recommend anything with C in it's name, just because the syntax of mql and the syntax of C is similar doesnt mean it is suitable for learning the concepts. You can try to learn C/C++ after you have successfully learned programming and have 10 more years time to waste, I'd rather learn practical useful languages like Python, Ruby, Java, if you love mathematics and statistics you should learn R and if you really want to go extremely low level and want to produce small efficient machine executables (writing dlls for metatrader) learn Pascal [FPC]. There is no reason to ever waste any second of your lifetime for C/C++)

After successfully learning the concepts of programming and having practically programmed something for some time you can again try to look at metatrader programming and everything will immediately be *much* much clearer and you wont be completely defenceless while trying to fight this beast.

ForexSaint, have you try to put your cursor/caret in the middle of the word/function/command you don't understand and then press F1?

Can I use the sleep command like this?

If not how would I make the EA sleep after the condition was met?




It closes the Trade so it gets to the glOrderClose() but it reopens another immediately.

If someone could show me how to put this sleep command in so it works, I would really appreciate it.

thanks

@7bit
Thanks again for a detailed reply...Yes its frustrating for sure initially!

@AdamnN
Thanks for that info

@Asgard
Hope some1 answers that query...here is a bump for you

Regards all

asgard, may I ask are you using this live or in strategy tester... Sleep will not function in the tester I believe.

Actually it does works in tester, but fastened