Global inside a Function
BlitzMax Forums/BlitzMax Beginners Area/Global inside a Function
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| OK, so a Global when declared inside a Function retains it's previous state when the Function is entered a second time, etc. But what about something like: Function MyFunc() Global file:TImage=LoadImage("file.png") End Function Is the LoadImage part only invoked on the first call to that Function (ie Var file is only initialised once) or would I basically be negating the usefulness of a Global inside a Function (Var file is reinitialised each call because of the '=')? |
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| It keeps its previous state, but you are simply letting it equal somthing each time. ie The firat time its run File doesnt exist. the second time file does exist, it equals whatever but you tell it to equal whatever again For the behaviour you state you need a doesit exist condition check arround it Edit. That doesnt sound right does it? |
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| Is the LoadImage part only invoked on the first call to that Function? Yes.Function MyFunc()
Global test:Int = Confirm("Does this get invoked twice?")
End Function
MyFunc
MyFunc |
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| Well thats me blown out of the water. Does that mean you cannot re-allocate a global within a function? If so is a global in a function a gloryified const? To use a Global as a real changeable variable Do I need to declare it out side a function? If I declare it as a field within a type, can I change it, or am I stuck with only the original value? edit Test:+1 works though dosent it? Even in Functions, so its only the declareation that is run once. O.K. I get it. Mind It would probably count 1,2,2,3 or something ;) Thanks |
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| A Related Question. When are globals created. IF I declare a global is it "Created" (Ie actual physical space given to it) at compile time or Run time. If at run time Is the global created when program flow passes it, or when the program "Initialises" (Cavat)Is a global created and initialised as a field for a type at the first instance of new for that type, or at the first refference to that type Thanks |
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Function MyFunc() Global test:Int = 1 Print test test:+1 Print test End Function MyFunc MyFunc prints 1 2 2 3 so its not as simple as you think |
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| @Chris, thats exactly what I said it would do in my edit.(Honest). Youve just read that, and posted yours to make it look like I didnt figure that out myself ;( (You are a meanie) Do you have any idea about the other one? |
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| so its not as simple as you think I might be missing something but example *really* is as simple as you think... Isn't it? |
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| makes perfect sense. The global is intialised once when the program starts, then it can be used like a normal global, but only withing that function. |
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| Hello. Yep, it makes perfect sense and is as simple as you think. Function called: start = 1 : prints 1 add 1 : prints 2 Function called: stays at 2: prints 2 add 1 : prints 3 What's the issue? Goodbye. |
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Print "Global in Function" For x = 1 To 5 Global_in_Func Next Print "Local in Function" For x = 1 To 5 Local_in_Func Next Function Global_in_Func() Global functest:Int Print functest functest:+ 1 End Function Function Local_in_Func() Local functest:Int Print functest functest:+ 1 End Function |
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| But why would you use a Global? Wouldn't Local be more appropriate? Would Local have the same result? I can see what the example is doing, but I cant figure out why? When the function is called for the second time, why is the Global not reinitialised and set back to 1? In my head, it the example should print 1, 2, 1, 2 So many questions... |
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The global-in-a-function behaves like any other global variable except that it is being initialised when the function is called for the first time and can only be accessed from within the function. So the example prints:Global in Function 0 1 2 3 4 Local in Function 0 0 0 0 0 |
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| Ahh, that makes sense :) |
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