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Active Forums => Programs => Topic started by: SMcNeill on December 02, 2019, 09:29:41 am

Title: Using _MEM to get/put arrays into UDT strings
Post by: SMcNeill on December 02, 2019, 09:29:41 am
Every so often, someone will ask, "Why can't we use arrays with User Defined Types?"  The answer to that, is of course, "No one coded BASIC to work like that, and the functionality hasn't been expanded for it yet."

Which, leaves us with trying to find a workaround for easy transfer of data via GET/PUT statements...

Here's the easiest way I've found to do this type of thing, and I thought I'd shared for those who might be interested:

Code: QB64: [Select]
  1. DIM b(0 TO 7, 0 TO 7) AS _UNSIGNED _BYTE
  2.  
  3. TYPE Whatever
  4.     x AS INTEGER
  5.     y AS INTEGER
  6.     s AS STRING * 64 'to hold b()
  8.  
  9. DIM foo AS Whatever
  10.  
  11. DIM m AS _MEM, m1 AS _MEM
  12. m = _MEM(b()) 'a memblock to point at our array
  13. m1 = _MEM(foo.s) 'and one to point at our user type string to hold the array
  14.  
  15.  
  16. FOR x = 0 TO 7
  17.     FOR y = 0 TO 7
  18.         b(x, y) = count
  19.         PRINT b(x, y),
  20.         count = count + 1
  21.     NEXT
  24. SLEEP 'So we can see what b() contains.
  26.  
  27.  
  28. _MEMCOPY m, m.OFFSET, m.SIZE TO m1, m1.OFFSET 'Copy our array to our User Type Variable
  29.  
  30.  
  31. CLEAR b()
  32. FOR x = 0 TO 7
  33.     FOR y = 0 TO 7
  34.         PRINT b(x, y),
  35.     NEXT
  38. SLEEP 'So we can see that b() is now blank.
  40.  
  41. m = _MEM(b()) 'point our mem blocks back, since CLEAR erased them...
  42. m1 = _MEM(foo.s)
  43.  
  44. _MEMCOPY m1, m1.OFFSET, m1.SIZE TO m, m.OFFSET 'Copy our User Type Variable back to our array
  45. FOR x = 0 TO 7
  46.     FOR y = 0 TO 7
  47.         b(x, y) = count
  48.         PRINT b(x, y),
  49.         count = count + 1
  50.     NEXT
  52.  
Title: Re: Using _MEM to get/put arrays into UDT strings
Post by: RhoSigma on December 02, 2019, 09:41:05 am
Code: QB64: [Select]
  1. CLEAR b()
??? Since when this is possible ???

Wiki doesn't mention this kind of usage.
Title: Re: Using _MEM to get/put arrays into UDT strings
Post by: SMcNeill on December 02, 2019, 10:04:34 am
Quote from: RhoSigma on December 02, 2019, 09:41:05 am
Code: QB64: [Select]
  1. CLEAR b()
??? Since when this is possible ???

Wiki doesn't mention this kind of usage.

Actually that's a classic "Steve Oopsie".  ERASE b() would be more appropriate to just erase the arrays, but CLEAR, in this case, works well enough here  (though the b() is ignored).

The ERASE statement is used to clear all data from an array
The CLEAR statement clears all variable and array element values in a program.


 
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