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<< Click to Display Table of Contents >> Navigation: ThinBASIC Core Language > Data types and variables > TYPE (or UDT User Defined Types) |
Description
Define a User-Defined Data Type (UDT), containing one or more member elements.
Syntax
TYPE MyType [BYTE | WORD | DWORD]
[STATIC] [MemberName AS TypeName]
[STATIC] [MemberArrayName[(nElements)] AS TypeName]
[...]
END TYPE
Returns
None
Member alignment
TYPE definitions may optionally specify an alignment of BYTE (the default), WORD, DWORD
•BYTE: each member will be aligned on a BYTE boundary - no padding or alignment is applied to the structure. This is the default alignment method.
•WORD: each member will be aligned on a WORD boundary. Any odd byte between members of TYPE will be automatically skipped and ignored.
The UDT structure is also padded with one trailing byte to ensure the total structure size is a multiple of 2 bytes.
•DWORD: each member will be aligned on a DWORD boundary. Up to three bytes will be skipped to accomplish this alignment.
The UDT structure is also padded with up to three trailing bytes to ensure the total structure size is a multiple of 4 bytes.
Remarks
thinBasic support any level of nesting types.
Elements inside a type can be:
•numeric: BYTE, INTEGER, LONG, QUAD, WORD, DWORD, SINGLE, DOUBLE, EXTENDED and CURRENCY
•string: STRING, ASCIIZ
•hybrid: VARIANT
•another used defined type (allowing nesting types inside another one) or UNION
To indicate a fixed string as UDT element use the following notation:
'...
DynStr As String * StringSizeInBytes
'...
To indicate a dynamic string as UDT element use the following notation:
'...
DynStr As String
'...
A dynamic string is represented inside an UDT as 32bit number so it will occupy only 4 bytes regardless of its size.
thinBasic will take care of memory allocation and de-allocation of dynamic strings.
A VARIANT element will always occupy 16 bytes.
STATIC elements
static elements are elements in common to all UDT variables derived from the same UDT TYPE.
They are not part of the UDT structure itself but are available to all UDT of the same type.
Static variables retain their values as long as the program is running.
Restrictions
See also
Examples
'---
Type MyRect
x As Long
y As Long
w As Long
h As Long
End Type
'---
Type MyData
Val1 As Integer
Val2 As Long
Val3 As String * 255
dynStr As String PTR '---Dynamic string
Val4 As EXT
Re As MyRect '---Note, a type inside a type
Val5 As QUAD
Val7 As Double
End Type
Dim Info As MyData
Info.Val1 = 10
Info.Re.x = 20
MSGBOX 0, Info.Val1 & "-" & Info.Re.x
'----Example of a type inside another type:
Type Vector2d
X as Double
Y as Double
End Type
Type Vector3d
Vector2d
Z as Double
End Type
dim foo as Vector3d
foo.X = 1.23
foo.Y = 2.34
foo.Z = 3.45