在QBasic中的用户定义的TYPE中使用数组

Question

I'm trying to learn QBasic to program on an Amstrad Alt-286. In one of my program, I use several user-defined types, sometimes TYPE arrays. In some of them, I want to declare an array like this :

TYPE TestType
    dataArray AS STRING * 4 'Since "dataArray AS _BYTE * 4" doesn't work (wrong syntax compiler says).
END TYPE

I then declare my type like this :

DIM customType(2) AS TestType

And as soon as I want to write in my type's dataArray like this :

customType(1).dataArray(2) = 3

The compiler tells me it is an invalid syntax.

Then, how to store an array in a defined TYPE? And how to use it?

Answer 1

There are two issues here. In QB64 you simply can't put arrays inside of user defined types. According to the QB64 Wiki's article on TYPE definitions :

TYPE definitions cannot contain Array variables! Arrays can be DIMensioned as a TYPE definition.

Besides that, your dataArray (declared dataArray AS STRING * 4 ) does not declare an array at all, but rather, declares a 4 character string. That's why you get a syntax error when you try to access elements of dataArray using array syntax. You can declare an array consisting of a custom type, like so:

TYPE TestType
    dataElement AS _BYTE
END TYPE

DIM CustomType(4) AS TestType

CustomType(1).dataElement = 3

This declares a 4 element array of TYPE TestType, each element containing a variable of TYPE _BYTE. That's about as close as you can get to what you're trying to do. Good luck!

Answer 2

The code you want is something like this:

Although you CANNOT do this in QB1.1, QB4.5, or QB64, you CAN do this in supersets of the BASIC dialect known as QB7.1(BC7/PDS), and VBDOS(v1.00):

TYPE testtype
    dataArray(4) AS INTEGER
END TYPE
DIM customtype(10) AS testtype
customtype(1).dataArray(2) = 3

Otherwise you could compress the variables as such:

TYPE testtype
    dataArray AS STRING * 8
END TYPE
DIM customtype(10) AS testtype
A = 10: B = 12: C = 14: D = 16
' compress variables into structure
element1$ = MKI$(A) + MKI$(B) + MKI$(C) + MKI$(D)
customtype(1).dataArray = element1$ ' store
' extract variables from structure
element2$ = customtype(1).dataArray ' get
E = CVI(MID$(element2$, 1, 2))
F = CVI(MID$(element2$, 3, 2))
G = CVI(MID$(element2$, 5, 2))
H = CVI(MID$(element2$, 7, 2))
PRINT E, F, G, H