Data Type question

[Scott Turchin]

I have a TYPE and I dim it as such perhaps:

mytype as TYPEA

Now, I test a function with this mytype and if the function fails I want to have mytype dimmed as TYPEB


Can that be done?


Thanks,
If so, got a nice lil' suprise to go in the source code forum, otherwise it will be tomorrow..


Scott

------------------
Scott

[Lance Edmonds]

You cannot do this directly, since the UDT must be established at compile time (or more accurately, when used to define a scalar variable, the DIM statement works as a scanned statement, not an executable statement). That is, the following is not valid:

IF condition THEN
  DIM a AS T1Type
ELSE
  DIM a AS T2Type
END IF

So how do you do it? Simple: The solution is to create a UNION of the two TYPEs, or a UNION containing pointers to the real UDT variables.

UNION Matter
  Potato AS VEGTYPE
  Banana AS FRUITTYPE
END UNION
..
DIM a AS MATTER
a.Potato.xxx = ...
a.Banana.xxx = ...

------------------
Lance
PowerBASIC Support
mailto:[email protected][email protected]</A>

[Bern Ertl]

Scott,

I'm not sure if it is possible, but would it work for you to make
a UNION of the two types with an identifier?

Ie.:

TYPE OrigType1
.....
END TYPE

TYPE OrigType2
.....
END TYPE

UNION OrigTypes
  FirstType AS OrigType1
  SecondType AS OrigType2
END UNION

TYPE NewType
  Active AS LONG 'Just a binary flag
  Data AS OrigTypes
END TYPE

You can check the .Active field to determine which of the
unioned types to access.....



------------------
Bernard Ertl

[Lance Edmonds]

Bern, we both responded at almost the same time! SNAP!

------------------
Lance
PowerBASIC Support
mailto:[email protected][email protected]</A>

[Scott Turchin]

Ah, OK IT's the union of potato's and banana's!! LOL...

In all seriousness here's what I'm trying to do, and now I know how I have to go about it, a Union may not work here but for future use perhaps

The new OSINFO!!!
'
'
'
%ERROR_OLD_WIN_VERSION = 0

Type OSVERSIONINFOEX
  dwOSVersionInfoSize As Dword
  dwMajorVersion As Dword
  dwMinorVersion As Dword
  dwBuildNumber As Dword
  dwPlatformId As Dword
  szCSDVersion As Asciiz * 128
  wServicePackMajor As Dword  'Word?
  wServicePackMinor As Dword  'Word?
  wSuiteMask As Dword    'Word?
  wProductType As Byte
  wReserved As Byte
End Type  


'
osviex.dwOsVersionInfoSize = SizeOf(osviex)
bOsVersionInfoEx = GetVersionEx(osviex)

If bOsVersionInfoEx = %ERROR_OLD_WIN_VERSION Then 'It failed
   lResult = GetVersionEx(osvi)
End If

------------------
Scott

[Scott Turchin]

PS, we all 3 replied at the same time!

I'll post the entire source to this tomorrow evening when I get it done, it's coming along VERY nicely!
This will be a MUST have for everyone, a new GetWindowsVersion, Microsoft style and very tight so far in the port to PB...


Scott


------------------
Scott

[Lance Edmonds]

Simple.

Create a fixed-length string of the longest structure size, and pass the address of the string to the API.

Next, create two UDT pointers, and point them to the string, then use the appropriate pointer to manipluate the data.

If you need to initialize a structure member with the structure size first (which some API's need), use the appropriate pointer to set the value.

ie:

TYPE sometype1
...
END TYPE
TYPE sometype2
...
END TYPE
 
... 
 
DIM z AS STRING * <the larger size of sometype1 and sometype2>
DIM p1 sometype1 PTR
p1 = VARPTR(z)
DIM p2 sometype2 PTR
p2 = VARPTR(z)
 
CALL someapifunction(BYVAL VARPTR(z),...)
 
IF condition THEN
  @p1.xxx = ...
ELSE
  @p2.xxx = ...
ENDIF

------------------
Lance
PowerBASIC Support
mailto:[email protected][email protected]</A>