DECLARE (General form)

Description

Sometimes is not possible to directly declaring an external function or sub because there is no way to know in which library it is.

To solve this problem, thinBasic allows declaration of external functions or sub without having the library name and alias. thinBasic will store all function or sub information for subsequent usage.

Syntax

DECLARE {SUB | FUNCTION} ProcName [([Arguments])] [AS ReturnType]

Returns

None

Parameters

Name	Type	Optional	Meaning
ProcName	String	No	Is the name of the function that will be used inside you script. This name must be a unique name not yet used as variable, as equate and not be a keyword or a reserved word.
Arguments		Yes	List of arguments to pass to function/sub. Arguments must contain the name and the type of the parameter the function/sub expects. Each argument can be preceded by an optional BYVAL or BYREF.
ReturnType		Yes	In case of function, the returning function type

Remarks

To be able to use the general declared function or sub, it has to be assigned a process address using DECLARE SET ADDRESS statement.

Restrictions

See also

DECLARE SET ADDRESS

Examples

'---

'---Standard API functions to get a function address. Those functions are used to simulate Petr SomeDirtyAPIToTellMeHandle function

'---

Declare Function LoadLibrary Lib "KERNEL32.DLL" Alias "LoadLibraryA" (lpLibFileName As ASCIIZ) As Long

Declare Function GetProcAddress Lib "KERNEL32.DLL" Alias "GetProcAddress" (ByVal hModule As DWORD, lpProcName As ASCIIZ) As Long

'---Commented line is a standard API declare for IsCharUpper function. We will not use this way in this example but ... (see next comment)

'DECLARE FUNCTION IsCharUpper LIB 'USER32.DLL' ALIAS 'IsCharUpperA' (BYVAL cChar AS BYTE) AS LONG

'--- ...we will tell thinBasic you are defining a generic function not jet initialized (ie, library and address are missing)

Declare Function IsCharUpper (ByVal cChar As Byte) As Long

'---OK, here we start simulating the assigment of the procedure address

Dim hLib As Long

Dim hProc As Long

'---First we need to load the library from where we want the address of the function

hLib = LoadLibrary("USER32.DLL")

'---If return value is NOT zero all is ok

If hLib <> 0 Then

'---Now we try to get the address of the prodecure inside the library

hProc = GetProcAddress(hLib, "IsCharUpperA")

'---If return value is NOT zero all is ok

If hProc <> 0 Then

'---

'---Here the new thinBasic functionality. It assign a process address to a generic previously declared function allowing subsequent calling

Declare Set ADDRESS IsCharUpper, hProc

'---So we are telling thinBasic that the previous declared function 'IsCharUpper' has now its process address

'---Now we try to use the new functionality that will tell us if a char is upper or not

Dim Char As String VALUE "F"

Dim AsciiChar As Byte VALUE ASC(Char)

MSGBOX 0, "OK. IsCharUpper for char " & Char & " returned: " & IsCharUpper(AsciiChar) & " (1=true and 0= false)"

Else

MSGBOX 0, "It was not possible to get the procedure address"

End If

Else

MSGBOX 0, "It was not possible to load library"

End If