Program Flow

The following constructs are available for controlling program flow.

If ... Then

If {expression} Then {statements1} Else {statements2} 

Evaluates the If expression and, if true, executes the Then statements. If false, the Else statement are executed, the Else part is optional - statements are executed until the end of the line.

If {expression1}
     {statements1} 
Else If {expression2}
     {statements2} 
Else If {expression3}
     {statements3}
Else 
     {statements4} 
EndIf

This form of the If statement allows for more than one line of statements. The Else If and Else parts are optional. The Else part is executed only if none of the If or Else If expressions were true.

While ... Wend

While {expression} 
     {statements} 
Wend 

A While loop continues executing until {expression} evaluates to False. {expression} is evaluated at the start of each loop.

For ... Next

For {variable}={initalvalue} To {finalvalue} Step {step} 
     {statements} 
Next 

A For/Next loop first assigns {initialvalue} to {variable} and then starts looping. The loop continues until {variable} reaches {finalvalue} and then terminates. In each loop, the value {step} is added to {variable}. If a step value is omitted, a default value of 1 is used.

This form of the For/Next loop allows you to iterate over all objects of a custom type.

Repeat ... Until/Forever

Repeat 
     {statements} 
Until {expression} 

A Repeat loop continues executing until {expression} evaluates to True. {expression} is evaluated at the end of each loop.

Repeat 
     {statements} 
Forever

A Repeat/Forever loop simply executes {statements} until the program ends, or an Exit command is executed.

Select ... Case

Select {expression} 
     Case {expressions1}
          {statements1} 
     Case {expressions2} 
          {statements2}
     Default 
          {statements3} 
End Select 

First the Select expression is evaluated. It is then compared with each of the Case expression lists. If it matches a Case, then the statements in the Case are executed.

If the Select expression matches none of the Case expressions, the statements in the optional Default section is executed.

Breaking Out Of A Loop

The Exit command may be used to break out of any For...Next, While...Wend, Repeat...Until or Repeat...Forever loop.

Using Includes

Blitz also supports the Include command. Include allows source code from an external file to be compiled as if it were part of the main program. Include must be followed by a quote enclosed filename. For example...

Include "anotherfile.bb"

Include allows you to break your program up into smaller, more manageable chunks.