Using _MEM to get/put arrays into UDT strings

[SMcNeill]

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()
7. END TYPE
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
22. NEXT
23. PRINT
24. SLEEP 'So we can see what b() contains.
25. CLS
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
36. NEXT
37. PRINT
38. SLEEP 'So we can see that b() is now blank.
39. CLS
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
51. NEXT
52.  

[RhoSigma]

Code: QB64: [Select]

1. CLEAR b()

??? Since when this is possible ???

Wiki doesn't mention this kind of usage.

[SMcNeill]

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.