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Statements

This section describes the collection of statements offered by HB++. All statements are reserved keywords that cannot be used as variable or function names.

Declarations

Some statements allow you to declare the constituent program elements, like functions and variables. The majority of these statements behave differently depending on where they are used in the program.

Variables are declared using the Dim statement. Used in a module, it declares a global variable accessible from anywhere in the project. Used in a class module, a form or a user control, it declares a member variable which can only be accessed by qualifying the variable name with an object instance. Finally, used in a procedure, it declares a local variable which only exists and is accessible within this procedure.

Methods, functions and properties are declared respectively using the statements Sub, Function and Property. Used in a module, they declare global procedures accessible from anywhere in the project. Used in a class module, a form or a user control, they declare member procedures which can only be accessed by qualifying the variable name with an object instance. It is not possible to declare local procedures ie one procedure within another.

Events are declared using the Event statement. They can only be used in a class module, a form or a user control.

The Declare statement authorizes the declaration of functions written in C and located in a shared library or in the operating system itself. It can only be used in a module.

Finally, it is possible to declare enumerated types and constants respectively with the Enum and Const statements. Contrary to other statement declarations, their effect does not depend on the location where they are used.

Apart from those residing within a procedure, all declarations must be preceded with one of the Public, Protected or Private scope modifier keywords. These basic access rules can however be overriden by the use of the Friend statement.

Control Flow

The control flow statements allow you to control the execution of your program. In the absence of such statements, program execution will always go from left to right and top to bottom. Although some simple programs only require this one way flow, all the power in a programming language is provided by its capacity to modify at runtime the statement order with conditional branching or loops.

The Goto, Call and RaiseEvent statements carry out unconditional branching whilst the If...Then...Else and Select Case statements implement conditional branching, that is to say only when a condition is true.

Loop statements repeat as many times as necessary a block of instructions. The HB++ language provides several loop control structures: Do...Loop, While...Wend, For...Next and For Each...Next. The Exit statement ends a loop prematurely.

Finally, the On Error Goto statement allows error handling, which directs the program execution towards a special routine when an error occurs.

Compilation Options

All the compilation options are set in the "Project > Settings" dialog box with the exception of the default array base index and warning display which are set independently for each project file using the Option Base and Option Warning statements.

You can also exclude certain sections of code from the compilation using the conditional compilation statements #Const and #If...Then...#Else. This is very useful for compiling different versions of your project without modifying the source code.

Other Instructions

Some statements simply carry out an action without affecting the program flow. In this sense, they appear more like functions than statements though they have a special syntax : the Let and Set statements affect a value or an object reference respectively and the Sort...On... statement sorts array or collection elements.

Reference

The statements described in this chapter are summarized below. On each page, the syntax described uses the following typographic conventions:

• Keywords corresponding to the statement appear in bold.
• Parameters appear in italics.
• Elements between square brackets [ ] are optional and can be omitted.
• Elements between curly brackets { } are compulsory.
• Elements separated by a vertical line | denote a choice of several elements.

For example the syntax { Public | Private } Enum indicates that the Enum keyword must be preceeded by either Public or Private.