Scripting Language Elements

Subroutines and Functions

Naming conventions

Subroutine and Function names can contain the letters A to Z and a to z, the underscore “_” and digits 0 to 9.  The only limitation is that subroutine and function names must begin with a letter, be no longer than 40 characters, and not be reserved words.

SEE  For a table of reserved words, see Functions, Statements and Reserved Words, in the Scripting Language Overview section of this manual.  

BlueZone Basic allows script developers to create their own functions or subroutines or to make DLL calls.  Subroutines are created with the syntax "Sub <subname> .... End Sub".  Functions are similar "Function <funcname> As <type> ... <funcname> = <value> ... End Function.”  DLL functions are declared via the Declare statement.

ByRef and ByVal

ByRef gives other subroutines and functions the permission to make changes to variables that are passed in as parameters.  The keyword ByVal denies this permission and the parameters cannot be reassigned outside their local procedure.  ByRef is the BlueZone Basic default and does not need to be used explicitly.  Because ByRef is the default all variables passed to other functions or subroutines can be changed, the only exception to this is if you use the ByVal keyword to protect the variable or use parentheses which indicate the variable is ByVal.

If  the arguments or parameters are passed with parentheses around them, you will tell BlueZone Basic that you are passing them ByVal

    SubOne var1, var2, (var3)

The parameter var3 in this case is passed by value and cannot be changed by the subroutine SubOne.

    Function R( X As String, ByVal n As Integer)

In this example the function R is receiving two parameters X and n.  The second parameter n is passed by value and the contents cannot be changed from within the function R.

In the following code samples scalar variable and user defined types are passed by reference.

Scalar Variables

    Sub Main

        Dim x(5) As Integer

        Dim i As Integer

        for i = 0 to 5

            x(i) = i

        next i

        Print i

        Joe (i), x   ' The parenthesis around it turn it into an expression

                     ' which passes by value.

        print "should be 6: "; x(2), i

    End Sub

    Sub Joe( ByRef j As Integer, ByRef y() As Integer )

        print "Joe: "; j, y(2)

        j = 345

        for i = 0 to 5

        print "i: "; i; "y(i): "; y(i)

        next i

        y(2) = 3 * y(2)

    End Sub

Passing User Defined Types by Ref to DLL’s and BlueZone Basic Functions

    ' OpenFile() Structure

    Type OFSTRUCT

        cBytes As String * 1

        fFixedDisk As String * 1

        nErrCode As Integer

        reserved As String * 4

        szPathName As String * 128

    End Type

    ' OpenFile() Flags

        Global Const OF_READ = &H0

        Global Const OF_WRITE = &H1

        Global Const OF_READWRITE = &H2

        Global Const OF_SHARE_COMPAT = &H0

        Global Const OF_SHARE_EXCLUSIVE = &H10

        Global Const OF_SHARE_DENY_WRITE = &H20

        Global Const OF_SHARE_DENY_READ = &H30

        Global Const OF_SHARE_DENY_NONE = &H40

        Global Const OF_PARSE = &H100

        Global Const OF_DELETE = &H200

        Global Const OF_VERIFY = &H400

        Global Const OF_CANCEL = &H800

        Global Const OF_CREATE = &H1000

        Global Const OF_PROMPT = &H2000

        Global Const OF_EXIST = &H4000

        Global Const OF_REOPEN = &H8000

    Declare Function OpenFile Lib "Kernel" (ByVal lpFileName As String, _

    lpReOpenBuff As OFSTRUCT, ByVal wStyle As Integer) As Integer

    Sub Main

        Dim ofs As OFSTRUCT

        ' Print OF_READWRITE

        ofs.szPathName = "c:\BlueZoneBasic\openfile.bbs"

        print ofs.szPathName

        ofs.nErrCode = 5

        print ofs.nErrCode

        OpenFile "t.bbs", ofs

        print ofs.szPathName

        print ofs.nErrCode

    End Sub