structures as parameters (ByValue)

[IceSoft]

I belive this is very important for some purebasic wrappers

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Structure myStruct
  a.f
  b.f
EndStructure

Procedure test(d.myStruct)
  Debug d\a
  Debug d\b
EndProcedure


aa.myStruct
aa\a = 10.0
aa\b = 5.0

test(aa)

Same for some return valueas as structures

[TomS]

Code: Select all

Structure myStruct
  a.f
  b.f
EndStructure

Procedure test(*d.myStruct)
  Debug *d\a
  Debug *d\b
EndProcedure


aa.myStruct
aa\a = 10.0
aa\b = 5.0

test(aa)

[STARGÅTE]

and for Return:

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Structure myStruct
  a.f
  b.f
EndStructure

Procedure test(*d.myStruct)
  *d\a = 10.0
  *d\b = 5.0
EndProcedure

test(aa.myStruct) 
Debug aa\a
Debug aa\b

but you will:?

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Structure myStruct
  a.f
  b.f
EndStructure

Procedure.myStruct test()
  d.myStruct
  d\a = 10.0
  d\b = 5.0
  ProcedureReturn d
EndProcedure

aa.myStruct = test() 
Debug aa\a
Debug aa\b

Right ?

but i thinks ist the same way

[KJ67]

It is a nice suggestion I like it , it would open up to clearer implementations of this kind of things.

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Structure Polynom
  a.i:  b.i :  c.i
EndStructure

Structure PolynomProduct
  a1.i: b1.i: c1.i
  a2.i: b2.i: c2.i
  a3.i: b3.i: c3.i
EndStructure

Procedure.PolynomProduct PMul(a.Polynom, b.Polynom)
  Protected result.PolynomProduct
  ;... code...
  ProcedureReturn result 
EndProcedure

But there may be a huge chunk of data on the stack, just imagine...

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Procedure.iso_image CatchCDImage(Drive)
EndProcedure

[IceSoft]

By reference:
Procedure test(*d.myStruct)

by value:
Procedure test(d.myStruct)

[STARGÅTE]

ah, you will work with "a copy" of structure in your procedure ...

[TomS]

Code: Select all

By Value: aa\a = 10.0
By Value: test(aa)

[Demivec]

Code: Select all

;by value
Procedure test(*d)
  Protected e.myStruct
  CopyStructure(*d, e, myStruct)
  Debug e\a
EndProcedure

test(aa.myStruct)

[IceSoft]

Code: Select all

;by value
Procedure test(*d)
  Protected e.myStruct
  CopyStructure(*d, e, myStruct)
  Debug e\a
EndProcedure

test(aa.myStruct)

This example works only for own written procedures. Not for external dll which want be wrapped for PB.

[Demivec]

This example works only for own written procedures. Not for external dll which want be wrapped for PB.

@IceSoft: You're correct, I had forgotten that you wanted this specifically for PureBasic wrappers.

[cas]

If you want to communicate with external dll then you must use AllocateMemory()/FreeMemory().

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Structure test
  x.i
  y.i
EndStructure


Procedure create()
  Protected *dat.test=AllocateMemory(SizeOf(test))
  *dat\x=15
  *dat\y=45
  ProcedureReturn *dat
EndProcedure

Procedure test_separate_copy(*struct)
  Protected privatecopy.test
  CopyMemory(*struct,@privatecopy,SizeOf(test))
  Debug privatecopy\x
  Debug privatecopy\y
EndProcedure

Procedure test(*struct.test)
  Debug *struct\x
  Debug *struct\y
  *struct\y=80
EndProcedure

Define *mystruct.test=create()

test(*mystruct)

Debug *mystruct\x
Debug *mystruct\y

test_separate_copy(*mystruct)

FreeMemory(*mystruct)

[IceSoft]

@cas,

As long you use *<varaiable name> as parameter as long it is always a pointer and this is byReference not byValue.

[cas]

Yes, but when you have reference then you know value to which it points, so i don't see a problem. Can you explain more how do you want to behave test() procedure in your first post? Do you want it to make separate protected d.myStruct which, when modified inside procedure, will not make changes in aa.myStruct?

Or you wan't to use C++ dll in PureBasic when it returns structure like this one(?):

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#define EXPORT extern "C" __declspec(dllexport)

struct DataStructure
{
  int x;
  int y;
};

EXPORT DataStructure TestReturnStructure() {
  DataStructure data;
  data.x=4;
  data.y=7;
  return data;
}

[OrangeJuice]

I think there was a good reason why C didn't allow that which i can't seem to remember right now. Maybe that is a slow thing to do?